As a master of one bitcion application. I think I have more details for why they run.

firstly,to run a site is expensive , including the code ,hosting, and human's time.

secondly, to attractive stable users is more expensive , for example ,I paid 2.75btc on this forum to theymos just for one slot to show just one week.


and the profit is not that great.and some times  there is no public income according to the game rule. the master's income depends on luck. like some dice and blackjack games.

so we must focus on the master's benefit , whether the master can make both ends meet at least. and withdraw as much as you can , to protect your btcs from site side accident.