I wonder if there will ever come a day where the average HN user actually understands how normal people use technology.
Just observe anyone in your social circle that does not "care" about technology and you'll see their reaction to a login prompt when trying, not rarely under time pressure, to access a service they haven't used for a while.
They will sigh, maybe roll their eyes. And who can blame them? The same goes for registering to a new service. Normal people don't use password managers, they don't have Bitwarden with auto-fill, nor do they ever "generate" passwords.
"Sign in with..." offers them a way out of a frustrating experience, it's the device telling them "Hey, would you just like to use this thing you're already logged into instead?" -- yes, obviously they would like that.