>> "What reason would anyone have for wanting to actively participate (not just poke-around like I'm sure quite a few employed professionals did) vs selling the exploits off on the dark web or just working in security for a company that pays a reasonable rate?"
The answer the your first alternative is pretty obvious: morals. That and not wanting to do jail time. To the second alternative I'm sure the people participating mostly have jobs or other commitments are are doing it for reasons other than the money.