I would guess it's because of regulatory compliance. You really don't want to release slots with a major payout but, and if you do, you want to be able to throw the blame at Unity.
Uhm, no? Unity is just the UI. The RNG algorithm runs on a centralised server.
The real problem is that the gambling business model is inherently incompatible with revenue sharing, because unlike a video game, you're paying money back to your customers every time they get a small win.
Let's say a gambler is wasting away $500 and getting back 95% every day and he plays until he runs out of money. Then unity would be getting $400 and the casino would be getting $100.
