I've seen some sites using this pattern in order to blur together the ideas of signing up and signing in. You enter your email address and then you are either

I've seen some sites using this pattern in order to blur together the ideas of signing up and signing in. You enter your email address and then you are either presented with your login method (Google / Microsoft / email), or else if you are brand new then you choose a method and go through a sign-up flow. But there are other reasons too. Google does this, I'm guessing so that users who are tech-challenged can be able to just focus on one question at a time? And then my bank does this questionable thing where they ask for my email first, then along with the password prompt, they show me a "security image" which is an image I chose when I made my account. I think the idea is that a phishing site would be less likely to know my security image, in which case I might realize something's up.