As far as I am aware cruise lines insist that the disabled person has someone with them to assist them, whether that would be a carer, relative or friend, but of course it all depends on the level of disability. If someone can manage perfectly well at home on their own, including getting out and about I don’t see any reason why they couldn’t have a cruise on their own if that’s what they wanted.
As far as cruises as a holiday choice for disabled folk, from what I’ve seen, they are brilliant. Virtually a new port every day so the scenery is constantly changing. There is always someone to chat to.
All ships have extra large cabins for disabled people, and I would always recommend one with a balcony for the private outdoor space.
There’s nothing nicer than waking up in the morning, pulling the curtains and watching the ship come into a new port waiting to be explored.
As others have said we have seen and chatted with lots of people on cruises in wheelchairs and they all seem to be having the time of their lives.