If I might generalize, I think as a nation we are not really into communal living.
A friend from the Middle East commented that in her private block of flats in London there are many older widows, who come and go during the day to the shops, hairdressers, etc., and some have family/friends who visit - what surprises her is that these residents rarely socialize with each other and certainly don't pop in and out of neighbours flats as they would in her home country.
I think that's just how we are, and how I'll be when am much older.
I'm sociable but a very private person and don't want to share a garden or a community room on a daily basis. A nod or a chat with neighbours is one thing but the idea of a retirement complex repels me, it really does.
Plus, as others have said, they can be a bugger to sell and the service charges are high.