There could in fact be greater marginal utility when most of those activities reside in one head and one person, instead of a team. Students attend prestigious universities to study directly with highly regarded researchers themselves instead of their TAs or adjuncts. Reviewing papers and serving in a conference committee requires one to know the ins and outs of a field. And so on...

Maybe most researchers could produce more/better research on their own without these responsibilities, but research-only positions are much fewer, especially in academia. Feynman also argued that teaching gave him ideas for new research.

I guess we should conduct studies to find out how best the society should organize research; optimal models might be dependent on the field or sub-field.

Incidentally, two of the Chemistry Nobel laureates this year made their discoveries when working in an industry lab and in his own private company.