Studio apartments aren't a thing anymore?
Pretty common in Europe and AFAIK not entirely unknown in high-rent Metropolitan areas worldwide (NYC, Tokyo etc.)
I was more talking about _not just_ young people. Studio apartments/small "bachelor pads" exist outside of pure age brackets or even affordability. Something bigger might not be available if you want to live close enough to work/city centre/etc. and/or it might be more common in your culture (Japan/Europe vs. US).
In other words: I don't see why a one-room situation should be restricted to young people.
A studio apartment is a one room apartment that usually has living space, bed and kitchen utilities all in one room. I’m not sure if you understood that. People tend to go for them because they’re cheaper.