I don't know how disability works in the civilian world, but for veterans who are getting money for a service connected disability (a disability or injury that occured directly from their time in the service) it's not based on whether or not you can work, it's based on a "loss" you suffered - both the kind and degree of that injury. They even have charts that will show lines thru different parts of the body with rating for your disability. Looks like one of those charts they have at the butcher to show the different cuts of beef. Lost one arm, you get this percent. Lost 2 arms, you get that percent, etc.. So even if someone CAN work, they are entitled to get disability of a certain percent for life. And even if they CAN work, they still may not be able to work in the same profession as they did before, and often can not stay in the military any longer.
So maybe this is the same in the civilian world of disability. People get paid for the loss they suffered thru their injury - as well as compensated for not being able to work in their profession any longer - but are fit and healthy enough to work at some kind of job - maybe a lower paying one. I don't know if that is correct or not though and may not be the case.
As for things like SS. medicare, unemployment, etc... I personally don't consider them entitlement programs as you had to earn them somehow - generally thru working a large portion of your life.