I agree, people think that you need to show proof of your birth certificate or something to play, it is a simple verification that you pass and its fine. I guess it is the fear that one day yo ucould be asked and this could have some governmental backing that will put you in trouble that makes them stay away from the place. I am fine with it because for me it is not illegal, I mean it technically could be, but I am not playing with "real" money based on our laws, hence it is not technically gambling. Laws here see this place, same as playing those slot games on your phone with game tokens, hence I am not worried about KYC anymore, I disliked even hated the decision to ask it, but I got used to it.
there are many minors who are playing and for this reason they do not like KYC, there are many people who do not have their own home and who are still at their parents' house even though they are minors and for this reason there is no way to deliver proof of residence because the water, electricity and internet bill is not in their name, there are many people who are afraid to hand over their passport on a strange website. That's why KYC is a big headache for most people, especially when we know that many casinos have anonymous owners so it wouldn't be fair for an anonymous casino to ask their customers for KYC.
The good thing about asking for a birth certificate or proof of service is to make sure of that, that it is not children who are in front of the PC, lately the world has been in a very digital axis, children have more access to internet tools, perhaps the pandemic has brought you to this world, although this means that we are in a process of protecting children, it is something that we all must sometimes accept for the common good, in my personal opinion, I have seen many programs where they deceive children, they end up being extorted, raped and sometimes killed, I prefer to give a KYC if this helps to avoid all this type of events, if we see it from that point of view, I know that many could make the exception.
Proof of service or birth certificate still cannot ensure that the person sitting behind the PC and playing gambling is an adult. For instance, if parents want they can provide all this kyc stuff and then give their children access to their screen/PC to gamble. In this case, you can still not avoid minors from playing gambling.
The only way to stop them is to force them to turn on their camera while playing, but why casinos take this hassle when parents themselves allow kids to play gambling.