If someone receives ssi Disabillity, what is the purpose of having a payee?

why does someone receiving ssi Disabillity need a payee? my son has been receiving it ever since he was 12 or 13 because of Attention Deficit Disorder and he has had behavior issues when he was in school. he is 18 now but not a responcible person at all. he rattles my nerves ALOT and i wish he could get his own place but im afraid he will spend his money on weed, liquor and stupid stuff and end up on the street. i was just curious, do you think Disabillity would allow him to get his own check if he will put in a request. or would i have to continue to be his payee and take care of him? because its some days i feel like i cant put up with his sh*t any longer.