Because, if a casino has 100 to 1k users (depends on casino size) who play with deposits, then they have only 1 to 5 users from Bitcointalk. So, it is normal to see the complaints from newbie users. I have followed numerous scam accusations here in the forum. If I remember it correctly, then I haven't seen anyone to submit a complaint with fake screenshots.
I saw some before. I cant remember the threads, but there are a few of them who makes a fake screenshots, but the fact is they use it to destroy the casino's reputation.
Since a casino is a business, this kind of attack is normal, but look at those highly reputable Bitcointalk gamblers who do gamble at the same casino. Why they don't complain? They haven't experience similar issues, I agree, but I don't still hear of a reputable Bitcointalk members giving a scam accusation against a reputable casino; most likely their case is solved immediately.
However, on newbies, it looks like the account was created just for destroying casino reputation, or it's just a marketing strategy.