Cats may not be capable of most of the things that dogs are used as service animals for, but can still be trained to complete certain tasks. They can open doors, fetch things, and they can also sense illness and symptoms of specific ailments (they can predict seizures pretty well).
Cats aren't just "antisocial" for no reason, they just tend to have a much higher sense of self preservation than dogs. They're also not emotionally void creatures, they very clearly capable of empathy. My cats have always been more friendly and cuddly when I'm sick.
They can also tell from body language when someone obviously doesn't like cats. So if you don't like cats because they're assholes it's probably because they can tell you think they're assholes and they think YOU are an asshole for it.