and maybe the positive side is that one day they will will get interesting offers from the gambling place which they can send to an email address or other.
this is true .
there are some sites that offers exclusive promotions but only to the costumer that have verified his account and verifying account can include a kyc .
To send offers and bonuses they only need an email, so knowing the identity for such purposes is unnecessary. Why should the casino care who you really are, when instead they can judge you by your performance on the platform (e.g. how much money do you spend, how often do you gamble), that would be fair.
On the other hand, I don't understand why everyone is so angry about these verifications, it's not like the casino will expose your data to the media, or tell on you to your government where gambling might be illegal. KYC can be long and tedious, but IMO there's nothing so horrible about it, if you're not a well-known criminal, of course