This is an interesting thread, because the reason I chose a slightly lower-ranked university (lower graduating pay, fewer research publications) with better student ratings was for those discussions. They were nothing like "let's have lunch in a nasty cafeteria" or "uh oh I'm failing help me manage my life!"
Instead, what I valued were conversations with professors about concepts, about the state of the field. I could bring in papers I had read. I could talk through an argument I wanted to make and ask them what was going on. I was a B+ student and that was working full time--I wasn't struggling to get concepts.
I could go to a professor and say "So, this is what I'm looking at in the paper, and this is how I see where it applies in the field, but what do you think the significance is? What further reading should I do? What was interesting about that article?"
Also, a lot of people who are A students still want to learn. My best grades, my As, were in classes that I had time to ask, "I got 95%, but this 5% seemed to be based on grammar and style, or was there something more substantial?"
I hated our flagship U for this stuff. Every time you went to a prof, they acted like all you wanted were points on a paper. I never got to talk to anyone--I was in my 30s and had a fellowship and was not struggling at all--not once, without them asking what I wanted. I walked out of one prof's office fuming after saying "I am here to discuss the ideas in this paper, not to beg for points--I don't need grades here, I am here to learn." Pissed me off. Still aced the final. I had an A in his class and I was thirty freaking five years old! God the arrogance. And that was most of my interactions with profs there. "What do you want...." Uh, what are they paying you for?
Lectures, I guess, not dialogue.
This paper validates my anecdotal experience well.
And no I never asked to eat in the lunchroom though it was great to go out for beers afterwards. The lunchroom! We weren't 15.