I think gambling sites only want huge profits with the number of members playing on their sites, regardless from of the data used for Kyc real or fake so far, because their dont care about age limit rules , I think to prevent minors from gambling should be the main responsibility of parents at this time, although it may interfere with their activities but parents should take the time for regular supervision, such as Monitoring children online activities regularly can be done without must to stop working, like checking browser history and using monitoring tools if possible.
If parents are not aware and can't save their child then there is no other way to save them. The site might not be prevented from using fake information, fake documents, or documents of parents and/or other family members. But if parents are aware of this then it might be possible to prevent them to engage on gambling.
Some of the site don't even require documents they just require you answer you are eligible or not. It's sad that parents cannot in all sense have absolute control over every single thing their children does, so they will only take control of that which they are aware of and for that which they aren't they may have no control control and can do almost nothing. I think there's a way some devices do allow for parental control and if that can be done then the parents can have some good level of control over the activities of their kids at once so for me it's basically not the parents fault as if its something they can handle completely, of course they will as some already Tey to take charge of that which they can handle because I believe no parents wants such for their kids.