To a first approximation no normal person uses a password manager (people find them extraordinarily hard to use; source: did trainings with a bunch of different cohorts), and the two solutions do not have "about the same level of protection". I watched a fintech company try to get people to stop relaying credentials through SMS with scammers, and that problem was practically insurmountable. I do not believe "autofill" is the fool-proof defense you think it is.