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.
There is nothing good about giving out your information, I know it is paramount to your money on casino but your privacy should be preserved to the barest minimum, the reason is that you aren't sure how safe is your documents and details when they are submitted into the hands of this organization, they could protect it very well in their custody and may sell it out if they wish because the people's information is big business, especially from reputable people.
Again, presenting a birth certificate will not solve anything, these things can be bought online, just like the hacker who bid to sell
Chinese documents worth 23 terabytes of data for bitcoin, he knows people will want to buy because they will use it to bypass all this restriction like this one we are discussing.