For example if you gave software developers a bunch of cash and told them to work on whatever they wanted, how many would go and build video games or invent esoteric programming languages (fun but not important) vs how many would want to build (or worse maintain) a system for the administration of taxes (less fun but very important). Hell, how many would even develop software at all vs just take up some other activity of even less value.
Therefor the best way to motivate these people is to extrinsic motivate them with money. However what happens if most of that money is taken as taxation and spent on people who sit around and do whatever they want all day? Do they still have the same incentive to do the boring but necessary jobs?
There will be luxuries some people want that are beyond the reach of those who live just on the guaranteed basic income. Those people will do the jobs that have not yet been replaced by technology to earn the extra money they need.
For instance, some people might want more living space. Some might want fancier cars than those people on the GBI can afford. Some might fancy a boat. Some might want a high end home entertainment system. Some might like expensive food and drink.
Open source software is an interesting example, but I think it mostly supports my case.
If you look at the projects out there, you can divide them into roughly 3 camps.
1) Projects that have a lot of paid developers working for companies or organisations that pay wages to their developers. So stuff like Android , V8 and Ubuntu would fall into this camp.
2) Projects that people were not necessarily paid to develop , but were developed mostly as a biproduct of something that they were or as a way to do that thing more effectively. "Scratch an itch" software effectively. I guess something like RoR would fall into this category.
3) Pure passion projects that were developed for fun. This is the only group that is purely intrinsically motivated.
The thing with projects that fall into camp #3 is that they tend to be stuff that the developer themselves found useful or interesting rather than something that necessarily serves society at large, though the two may sometimes intersect there is no guarantee.
If you don't make peoples incomes at least somewhat dependant upon the software they develop you will see far more camp #3 projects than camps #1 or #2.