Prevent from harming? What are you talking about? Would you like someone to follow you in every step, telling you what you are supposed to do and stopping you from doing dangerous things? Don't drive fast! Don't do extreme sports! Don't buy cryptocurrency! At some point it's fair to ask if we're adults or not? Being of age used to mean that you're able to decide for yourself and don't need mommy and daddy anymore.
If you gamble with money you don't have, you are mentally challenged, and for that reason it's better to have banks cut people off, than no one doing anything to prevent these people from harming themselves.
I don't need anyone to tell me anything because I'm not making stupid mistakes like that. You have to accept that it's not
your money that you are gambling with, but the money these banks are willing to loan you.
Being of age doesn't mean anything when you as person can't think and act like anyone of age.