The professor can't interact with _all_ their students. It's not uncommon for a prof to have 600+ students. If she interacted with each student just one minute per week, that's at least ten hours a week.

The current system is actually fairly good: profs hold office hours, and motivated students self-select for prof-student interaction.

Also, when a TA does the student interaction instead, then both parties benefit: the TA benefits from basic practice explaining concepts to students etc.