If you think the majority of people would just lay their lives to waste because they don't need to doing the bidding of others just to survive, then you are wrong. 99% of able-bodied and able-minded adults would not succumb to idlery.
Applying for SSI/SSID is an incredibly dehumanizing process. It takes over a year if you are lucky. You will be denied for any reason they can possibly find. It is guaranteed you will be denied for your first application. You have to prove you are disabled to them (disgusting really). You must have documentation. It goes on and on, but they honestly hope most applicators either die in the interim or just give up on 'improving themselves'.
Really, if there is a miniscule amount of people who will abuse the system it does not at all outweigh the good it provides. If your qualm is with said abusers, profile, detect, and prosecute them. Society is not going to collapse.