Yeah, I've lived in houses with one toilet (which is the main issue) for more than three people, and that's why I refuse to do it now. It wasn't bad when we were kids and there were five of us per toilet, but when I was in college, there was nothing like having to hope my room-mate would clear out quick enough for my bladder's tolerance for being kept waiting.
When we lived with the inlaws, well, I don't even want to get into the details about the bathrooms and showers in that flat. There were two toilets though, one being outside (flush). At one point the outdoor one (the one I used most of the time) was out of use. It didn't last long. I wasn't going to put up with my MiL's lengthy morning ablutions whilst I stood outside waiting to use the toilet. Not to be mean, but the over an hour a day she spent in the morning on her hair, make-up, and so on really didn't make that much difference except to those of us waiting to use the lav.
Different people have different tolerances, and there are some things I won't deal with. I can easily share the toilet with my husband (something some women in the States wouldn't ever deal with) and if we ever had to take on a room mate or had a child, maybe one other person. Above that, I'd beg, borrow or steal to get the money for either a rental upgrade or, if we owned, the money to at least put a toilet and basin in. Maybe it's because I have a really sensitive bladder (and always have), but it seems to me the more demand a for a toilet, the more some people seem to take the mickey about making sure it's available when people need it.