Specifically signing in with a consistent persona. All of these link to an actual "work" identity. Sometimes I want some customer support. Other times, it's a gaming identity, or a writer identity.

Part of the problem is that communities can get really nasty, worst case going as far as writing bad reviews at the place you work at. So it's useful to containerize your identity.

Reddit actually does this very well.

I explicitly avoid all of those and am willing to do the extra two clicks to get a real account.

I have no idea how long these random companies will keep providing auth services, I don't want to be part of the mess when they inevitably stop the service or start charging. It barely solves the account fragmentation problem because every website supports a different random combination of providers. It centralizes everything more than it already is, further increasing your dependence on these companies. Not to mention the tracking.

But the biggest thing is that with a native account I know that I'll be getting all the features of the app and everything will work normally. There have been too many times where I've experienced "your account does not support this feature" because of a botched external auth integration. Remember when Spotify users with Facebook sign-in couldn't change their name from the default string of random characters?

No thanks, the "effort" is more than worth it for me.

Can I sign in as a guest/anon user?