Earlier quoted context omitted.
I am unlikely to use your site if it requires me to use a Google or Facebook login. Those companies already have too much power to fuck my life up, I have no interest in giving them any more.
While I'm sympathetic to your viewpoint and to a large degree share it, you are among a vanishingly small minority to not use a site or service just because of social login. 'jfaucett probably is fine sacrificing losing this small minority.
precisely. In my experience, this small minority can actually be subdivided broadly into two groups: those with very high data privacy concerns and scammers/spammers. It turns out that in my experience, the high level data privacy concern people have been the vastly smaller of the two groups, so at the end of the day you are sacrificing a tiny fraction of a fraction of potential users while simultaneously removing tons of scammers from your platform. Admittedly, the ratios probably vary depending on the particulars of your pricing models and potential scam vectors that can be applied to your software, also other factors such as local attitudes toward data privacy (my experience has been in the EU). You can also increase sign-ups by a large portion of the data privacy people by simply doing a lot of things to make your services legit i.e. have domain names registered to the real business or contact person, force https, have a high level overview of your terms and services that clearly and succinctly states how you use users data, have a verified https certificate, etc. But in general "social login only" has been so much better for me than mixed or only email logins I really would not want to go back to the alternatives.