Why are uncontacted peoples still so primitive?

It's hard to imagine that in this day and age there are still tribes of people in this world that have little to no contact with the rest of humanity, and live in either voluntary or enforced isolation. (Those tribes who live in voluntary isolation know that other people exist in other parts of the world, and might even know that they are much more technologically advanced, but have decided for one reason or another to remain as isolated as possible and not have any contact with the outside world. There are also some tribes who have little to no knowledge of the rest of the world and are still living isolated mainly because they are being protected by the countries where they reside in, which ban contact with those people.)

One striking feature of these people is how extremely primitive they are. Pretty much without exception they live in huts made of straw and branches constructed directly on the ground (ie. they are floorless), and their most advanced weapons are primitive bows and spears. They haven't developed even so much as primitive agriculture, and are still pure hunter-gatherers.

This feels a bit strange given the fact that these tribes have usually existed for hundreds and hundreds, probably even over a thousand years, if not even longer (especially those living in remote islands who have had no contact with anything outside the island for probably thousands of years).

One would think that no matter how isolated these tribes may be, over hundreds and hundreds of years they would develop at least some techniques and technology more advanced than a primitive hut and a bow. Woodworking, houses made of wood or even stone (with floors, if not outright elevated floors that keep rainwater out), some form of agriculture (no matter how primitive), better wooden weapons... something. But no, they still live pretty much at the same technological level as they did a thousand years ago. Not even a modicum of technological advancement.

How is that even possible?

Moreover, it is said (although I have not corroborated this) that not a single invention has been done in sub-Saharan Africa for over ten thousand years, and every invention that we know of has been developed in Europe, the Middle-East and China, and a few other parts of the world.

Putting stupid racist theories aside, some people present one possible theory, and I would like myself to also present another theory. It may be one or the other, or perhaps a combination of both. I'll present first the commonly suggested theory and then mine.

1. Climate

Notice another striking feature of these isolated tribes: All of them, every single one of them, lives in a very hot and humid part of the world, in the tropics. I'm not aware of any such isolated tribe that would live in very cold or outright arctic conditions. (There certainly are very remote villages in very cold locations that are somewhat primitive and somewhat isolated, but they are not that isolated from the rest of the world in this sense, as they tend to have regular contact with the outside world and a significant amount of technology imported from the rest of the world.)

Many people also comment that the average culture in very hot countries with a very long history, especially Africa, has a noticeable difference to the cultures of very cold countries. In the hot countries people seem to have very distinctly a preference for instant gratification rather than delayed gratification. With "instant gratification" I mean that whenever they have the chance to get something they want it immediately, they want to consume it immediately, they want to use it immediately. Or to put it in another way, they tend to not plan for the future. They tend not to store nor invest (and I'm not here talking solely about money, but about everything).

This is in contrast with people of very cold climates who, by the very necessity of their climate, have had to always plan ahead because of very harsh and cold winters, when nothing grows, nothing can be gathered, and even hunting is significantly more difficult, and overall survival is a lot more difficult than in the warmer periods of the year.

People living in very cold climates simply cannot afford instant gratification with everything. Since time immemorial they have had to plan ahead, principally and especially about how to survive the winter. Instead of immediately using and consuming everything they get their hands on, they have needed to think about how to ration, how to store, how to make sure that they have sustenance for the long months when they possibly can't even go outside, much less get any food.

It is theorized that this having-to-plan-ahead has instigated inventiveness. Suddenly people have had a good motivation to build better houses, to invent more efficient ways to hunt, cultivate and harvest, more effective ways to store food for the winter.

While this theory might be plausible, I don't think it can be the sole explanation, and that's because it doesn't explain why so much technology and inventions were developed in the Middle-East and Arabic countries, which tend to have very hot climates.

(One possible answer to this objection is that it's actually similar to the cold climate in that the living conditions in most Middle-Eastern countries tends to also be very harsh, just in the opposite end of the temperature spectrum, and thus people can't just afford resting on their laurels and live like pigs, and have had to be inventive in order to survive. This is in contrast with tropical climates where living conditions are not that harsh because of abundance of water and wildlife.)

2. A money-based economy

My own suggested explanation for this is that those isolated tribes do not have a money-based economy.

I posit that the invention of money-based economy is what has allowed some cultures to advance so much technologically, to make so many inventions and so many technological innovations.

You see, in primitive cultures without a money-based economy everybody has to essentially work for their direct sustenance. They have to hunt, gather, cultivate, harvest... Every day, almost all day, they have to do stuff to get food, to get sustenance.

This gives very little free time. Free time that could be used for thinking, pondering, tinkering, experimenting, researching, innovating. When all you can do and think of is where you get your next meal, that's not very motivating for thinking if you could perhaps do some woodworking to build a bigger and stronger house, or to invent a machine to do arithmetic for you.

Money-based economy changed this radically. Suddenly you could earn a big bunch of money if you worked hard or got a good idea, which would allow you much more free time. Moreover, rich people could employ other people to do research, development and inventions. Suddenly people could do technological advancement as their primary job, not having to be out there hunting or harvesting crops.

In other words, money-based economy both gave people a lot more free time in order to do non-survival-related stuff, and to even work primarily doing such non-survival-related-stuff.

These primitive isolated tribes do not have this luxury which is why, I surmise, they haven't advanced technologically in a thousand years.