If you're only win some amount like x5 or x10 from your deposit amount and the amount is less than <$1000 it's only tiny amount for the casinos. Of course there's no reason why they should scam you for tiny amount while they can scam more money than that. 1xbit is selective scammer, if you only deposit for $100-$500 and win big amount money e.g above 1 Bitcoin, and they let you withdraw... post it here.
This won't necessarily prove that they aren't scammers and are completely legit or anything. As you said, they selectively scam their customers.
They could process withdrawals ranging from hundreds to thousands of dollars successfully without any issues while scamming other gamblers simultaneously which is pretty smart if you think about it.