It is also an incredible inefficiency; a waste of both the author's and the researcher's time.

If there were an inherent reason they needed personal contact-- say, a geologist had a question about what kind of signature a rotating radio transient might impose on rock strata of a certain composition, a question tangential to the topic of a paper, but which the author might know-- that would be different. (Yes, I realize that it is a silly question.) That would be different.

One of the things I think we desperately need is the skills of generalists that are enabled by open access. Some people have an uncanny knack for interdisciplinary work/phenomenology, but with heavy barriers to access we can't utilize those people properly.