The two of you must have had a different experience than I. At least for my classes, fundamental stuff that hasn't changed in decades was taught in big lecture halls- single variable calculus, physics & chemistry 101, etc. Then as you advanced in your discipline, class sizes shrunk, all the way down to 5-10 pupils in some of the most specialized classes, which was where the close interaction with the teacher was most valuable.
Most undergraduate students aren't ready to participate in research. Of those that are intellectually prepared, few have the grit/persistence required.
More indirectly, few have any kind of serious investment in the research. In college I volunteered to help on a plant study. I was assigned to meticulously clean dirt from dried plant roots and weight each plant. For like four hours at a time. Thousands of specimens. It needed to be done, but I had no investment in the project aside from general excitement, so I just didn't care enough to suffer the drudgery week after week.