Sweden.
When I went to university, I had a student apartment. It was cheap and tiny, 18m^2. There was a slightly cheaper student housing option where you would share a living room and a kitchen with other people, but in those everyone has their own private bedroom and bathroom with their own front door. Some of my friends rented regular, small apartments in the city. Some shared apartments, but always with existing friends, people they'd known for a while and knew they'd get along with.
As you exit university, you lose your student housing, but if you have a job you can usually afford a small apartment, a studio or a 1BR. The amount of people sharing an apartment with others at this age is even lower.
Eventually, most people get into a relationship, and move into a larger home as needed, and this is where the attitudes between the US and Sweden are the most similar, if you have a family and kids, most people get a house of their own.
One difference between the US and Sweden though is that there is strong political pressure for construction companies to build small apartments. In the US there's political pressure to build low-income housing and accessible housing, but for some reason no pressure for making sure everyone gets their own apartment?
That's still leaps and bounds from the American custom of advertising for a roommate, interviewing a bunch of candidates, and then picking one. There's a reason the "crazy roommate" is a trope used in American TV and cinema.
That is completely alien to me. :-)
> Living by yourself quickly becomes very lonely
Funny, that's a complaint I don't think any of my friends and acquaintances have had. I'm just gonna chalk that up to culture as well.
1. Live with parents
Not something most people want to do past a certain age.
2. Live with friends
People seem to be moving abroad more these days leaving you with friends all over the world, but possibly none currently in the city you live in.
3. Live with significant other
Fine until the relationship ends and someone needs to move.
4. Live with strangers
You meet new people, if you don't like them it's easy to just move somewhere else and try again.
The '6 of us in a 3 bed' thing is insane and unrelated to the living with strangers point.
Where are you from that sharing a home with strangers is such a strange concept? Who have you lived with instead? If you were able to afford your own place you're either very lucky or live somewhere very inexpensive because even in smaller cities that's not an option for most people.