[0] https://www.trenitalia.com/it/le_frecce/frecciarossa-per-il-...
https://www.messynessychic.com/2014/12/04/that-time-the-pari...
I've never seen it on a purely urban or suburban train within Europe, but then encountering a "screamer or crazy person" is something that happens perhaps once a year, and only if travelling at unusual times like at night.
However, if one car costs $3 and the other costs $6, the person who is statistically likely to urinate on the seats is more likely to pick the $3.
I will honestly pay double fare just to sit in a car with others that can afford to pay double fare.
I've been to other countries where the public transportation was amazing, and unsurprisingly there were almost zero people urinating (once in Japan I saw a drunk salaryman passed out with his pants around his ankles at a station and he was quietly whisked away less than a minute after I spotted him) so it's not as if a nice train system for everyone is some pipe dream that can't work in reality.