I knew people in the 80s who didn't have a landline phone.
We had a landline in the 70s and 80s but until the mid-80s it was a 'party' line - that is, we shared the line with a house over the road. We had different numbers so we didn't get each other's calls but if we wanted to dial out, instead of just lifting the receiver, there was another button to press underneath the rotary dial and if the people over the road were using the phone, you would hear them talking and you had to wait until they were finished.
It was cheaper than having your own landline but I believe the reason for it was something to do with a shortage of lines when STD codes came in in the mid-1970s. Up until that point people had to go via the operator to phone anyone outside their area.
That was the 70s/80s, though, not the 1990s.
In flats and what we'd now call HMOs, communal phones were common in the 1990s. When I was a student in university accommodation, there was one phone for the entire block that could receive incoming calls, so you were reliant on people taking messages or coming to fetch you if your room was nowhere near it.
If you wanted to phone someone, of course, you had to use a payphone - there were a few scattered round the place and by the 90s most people used phone cards - prepaid cards you could buy in various denominations.
In the mid to late 1990s, along came the internet and woe betide you if the household you were trying to call had a keen user because the modem would tie up the landline!