The same actually applies to bookmakers, if you choose a bookmaker that always pays out nicely for years, but then suddenly does not pay out if it concerns a large amount, then you can also have your reservations about that as a player. Trust is important to customers in the gambling world.
They should be trustworthy even in a small amount, gambling sites should address issues as they come, and even if the issue is small because gamblers are quick to notice and will not ignore and remember their action, you are right to trust is very important and every project and gambling site should make it as their corner stone if they want to continue doing business.