There is so much unpaid labor that big tech depends on. If they had to fairly pay for all that work through donations or otherwise they would go bankrupt, every single on of them. Big tech grew so massive because on open source, but it also helped open source grow. big tech will also die because they are increasingly just a leech-like middleman that just sits upon a mountain of free work and whose relative sliver of code contribution in comparison to the total code in a product is getting smaller and smaller and big tech is therefore increasingly a burden and not a asset to societies, economies and other companies.

Governments should be funding the most popular open source software that the world relies on

profits of business have always been dependent on governments funding research and free work done by individuals to turn a profit. Open source is nothing new on this regard.