My problems with apartments are that 1. you can't add tenants, 2. you can't use it as fc and 3. there only is small ones.
If your fc has the money for a large house and doesn't care much about having a neighborhood, apartments still can't give them instanced housing. And instanced doesn't mean one room cut off from everything. It can mean an island, or a more complex room with a balcony, or a cabin on a flying rock somewhere in abalanthia. The instanced housing we got that is still limited and sold out on some really big servers is probably the cheapest possible solution to implement it.