In some way these guys are "investing" in these YC companies' future, hoping that when they grow they will stick with DO. YC has good track record so it's relat

In some way these guys are "investing" in these YC companies' future, hoping that when they grow they will stick with DO. YC has good track record so it's relatively a good bet, whereas if they did it with any rando startup, they'll probably lose tons of money (statistically 99% of the startups die). Remember this is a company not a charity.