I think it might just come down to bad training in some casinos and maybe misinterpreting the EU directive. In all fairness though these stupid EU directives are prime for misinterpretation due to their vagueness. So red tape rules I guess.
Not picking on you
@osulle, just using your post as a reference point
While it is true in many cases, that EU directives are somewhat vague, it should be noted that a directive is primarly a legislative instruction in achieving a desired result. Anti-money laundering rules are global and the standars are mostly set by FATF. Being a member in the EU or not has little to do with it.
When it comes to online casinos, there's always the licensing authority angle. It doesn't help, that the AML requirements are often tied together with RG regulations (by the regulators). And then used as a license requirement.
I do agree that some operators confuse AML and RG. Or they don't, but are lacking in informing the player of their reasons for requesting documents. The big problem is the way RG is used as an indication or suspicion of illegal activities (ML). The whole AML system is built on the consept of "guilty unless proven innocent". But the whole RG aspect gambling has nothing to do with illegal activies of the player. It's somewhat an ambidextrous way for the society to allow and frown upon gambling at the same time.
It would be great, if the regulators made a clearer distinction between these issues.
It seems that the OP's case was classified under RG at the operator's end. That would make it an issue mostly relating to licensing requirements, which really has little to with the EU or AML regulations as such.
The "steady income" argument used by Casinoroom is OP's situation is a moot point. When did it come necessary to have "steady income" to play in a casino? The same problem comes with recycling winnings. If the funds are clear and not of illegal origin, then it should be up to the adult individual to choose how they spend them. It should not be up to any operator and neither any regulator. Problem gambling should be dealt with in another manner.