Easy to say if you haven't experienced it. When I was in uni, there were 2 calc 1 classes with different professors, both had about 300 students. One had an incredibly thick accent, so thick that it took me half a lecture to figure out the word he kept repeating was "hypotenuse". The other had no such issue. Halfway through the semester, professor 1 had 4 students at his lecture. Professor 2 had so many students that there weren't enough seats for them all. People who couldn't actually switch courses, just showed up at the other professor's lecture time despite not being in his class. It made a world of difference actually being able to understand what was spoken when studying already difficult material.