<p>I think it depends as much on the student as on the prof (s). My shy S has cultivated very good relations with a few profs, most of whom he had in small classes. He did not bother trying to talk to others, especially those in large classes. However, he told me that one of his profs, in a class of 100+, required every student to come and see him.
His roommate, on the other hand, is a born schmoozer and has managed to talk to profs in large lecture classes at least once a week and befriended them, including world famous profs. He’s lined up some interesting internships through them.</p>