Why have researchers been so ready to campaign against for-profit academic publishers such as Elsevier, Springer, Wiley-Blackwell, and Taylor & Francis/Informa, but not against for-profit platforms such as Academia.edu, ResearchGate, and Google Scholar?
Because “someone’s making money” isn’t what bugs researchers. What bugs researchers is being impeded from the business of doing their research.
Paywalls and subscription fees obstruct academics trying to do research.
Platforms like Google Scholar facilitate research. I could not do my job half as effectively if Google Scholar didn’t exist. Academia and ResearchGate haven’t been as useful yet, but I have never felt the frustration in using them like I have when I’ve hit the “pay now” screen for that article I want to read..
It’s also worth noting that the original question contains an assumption: that campaigns against for-profit publishers are major academic movements. But those calls for boycotts have...well... not exactly left those business struggling. They are still highly profitable, and show no visible signs of worrying that academics are going to stop submitting papers to their journals.