>Those aren't lost sales. Nobody sane would pay $40 or so for a 20 pages paper. Even if Scihub didn't exist. Publishers know nobody pays that. There are other options free for academic, such as subscriptions universities pay for or inter-library loans.
This may sound tinfoil hattish, but ever since I was in school i've believed it's to keep knowledge out of the hands of the poor. Accessing journals is basically out of the question for ordinary people, unless they go to a university library, or spend money they're not going to spend, almost all reporting on science is complete and utter garbage that at best, gets most of the facts wrong, at worst misrepresents or distorts the article being reported on completely.
I don't like making blanket statements, but i've noticed, many people lack even basic knowledge of scientific methodology and almost see it as a black voodoo magic or something. Average people have no real way to verify scientific claims made by media even if they wanted to.
I have to be honest too, going through school, this attitude was prevalent among my teachers, that scientific knowlege was best left to scientists to interpret for average people. Everything around science has a 'it's our special club' thing going on designed to trickle only what information scientists and authorities deem necessary.
Hell, the data from my own project was locked away by the government behind a paywall, despite it being funded by tax money under the stipulation in our grant that our results and data would all be made publically accessible and we were only studying small mammals.
Science, especially publically funded science, should be available for everyone. I've never agreed with the idea of hidden knowledge. Human progress comes from humans learning and sharing knowledge with eachother. Keeping knowledge locked up for a special elite cripples the progress of humanity.