That’s not true. Source: University of Warsaw. Poland. Not Illinois. I’ve had office hours with world-class mathematicians. Those office hours were required of every lecturer and TA.

At a top university in Scandinavia, lecturers will rarely respond (or even read) emails from students.

"Office hours" did not exist, but TAs attend scheduled labs/exercises.

Professors were even under instruction to not engage with students outside of scheduled and budgeted time.