I think the problem with thinking of it like an investment is there is a 0% chance of personal, direct, return on your investment. It may benefit society and you may even benefit indirectly due to the benefit of society, but you would not be entitled to direct return on your investment. In that case to me it seems like a non-starter purely as an investment. There would also be very ambiguous (if any) accountability of the ROI with lots of hand-wavey things for ups and downs. You also can't re-invest anything that is invested in this manner, like you can with other investments. You can't rebalance or shift investment around once it's happened. So there seems to be a huge sunk cost the principal is unrecoverable.
Maybe it's just too complex (right now) to calculate an expected ROI so it tends to sit more on the side of speculation than investing. It may seem like a good thing to do, but we're really just guessing.
> $100 per month justifies at least $50,000 in additional investment, $100,000 if you count compound effects
That seems like a total guess without a source.