Sometimes not having a demo play pisses me of

But it doesn't really matter a lot.
Something like this is ok to experience because demo will help channel gamblers experience to the right expected way they would have wanted to, but most times this comes in forms of ads that can also be annoying whereby users may find the contents uninteresting.
I would be annoyed if the casino will hold the funds without having any reason that makes sense.
Casinos don't normally denies gamblers access to their account except if the law is breached or been suspected for unusual acts, this is mostly the gamblers fault if you find out at the end.