Ask HN: Why do many websites use a sign-in code instead of a password?

I've noticed several websites that exclusively a single-use login code for authentication. This is a 4-digit or 6-digit login code sent via email instead of a password, it's not 2FA or a passkey. (I would rather they don't do this as it means I have to open my email instead of using a password manager.) Some of them also send a magic link. Examples of websites that appear to do this exclusively (no password): substack.com, medium.com, geoguessr.com, bandsintown.com. There are also websites that default to this but will also accept passwords (e.g. spotify.com). There are also websites that will accept either a passwords or login code, but if you enter a password then they require a login code anyway (e.g. homedpot.com).

Is this becoming more common, and if so why?