Their motivation is immediately clear to me. If you use "I forgot my password" you don't have to remember a password. And it doesn't even make your account less secure, since that pathway was going to be available to attackers regardless. I've seen websites that make that their default flow, arguing (implicitly) that having passwords at all is pointless when you can just email someone a login button, skipping a step.

Personally, I hate it. I don't trust my email, hate that it's a single point of failure for dozens of accounts (it's not "2FA" if the second factor is the only one I need), and I'd prefer to log in with a password without any option to reset it. But alas.