While you're probably right that hitchhiking isn't as popular as it used to be, it definitely hasn't practically disappeared. I still keep doing it more or less frequently, often with my kids
, in Poland as well as in other European countries*, mostly coming back from some village or trailhead in the mountains with little or no public transport. And it does happen to us to take hitchhikers too, when we are "on the other side" - once we took a guy with a paraglider who landed in a different place he wanted to!
Anyway, hitchhiking is still alive in Europe
* and outside Europe too, sometimes in quite remote places