And if you don't turn it into a business, it doesn't, even though a lot of people may find your hobby project interesting/useful.

What's the commercial value of a free live streaming app that captures evidence of a (say, for the sake of argument) a police assault, which eventually leads to a riot?

GDP is like a summary of all relevant execution paths through code. But it's really a list of paths that are considered relevant for traditional reasons.

It's not a complete picture, and in many ways it isn't even a useful one - because there's a huge implicit social morality tied up in econometrics that makes assumptions about social value.

Those assumptions are becoming less and less relevant for all kinds of technological, political, and even economic reasons.