Most retarded, mentally unstable/insane, autistic people etc. don't have that much of a social life, but I do.
As usual, generalizations from the General.
In many cases it's not the handicapped person who choses to be socially isolated, but parents who fail to realize the capabilities of their child or parents worn frazzled taking their child to the different functions.
Our daughter has mental retardation. In the "Bad, Terrible, Horrible, Evil" USA there are numerous social outlets for handicapped people. The Down Syndrome local organizations have events. Our local government has an adult social group for special needs adults. There are 2 private social clubs with waiting lists for members. Sports activities include Special Olympics, Cerebral Palsy swim team, at least 3 bowling leagues (with waiting lists)
The special school that the Princess Royal attended had a spring dance, cheerleading, a fashion show, student council, sports, choir and bells, and Best Buddies where average high school students go to plays, holiday parties, baseball and basketball games, etc. with the students.
And all this is available in the very non-progressive Deep South.