But then you can start listing non-HTTPS sites, too. You disclose your password in plaintext to many servers every time you login on those.
"But what if someone hacks your email, they know all your passwords!"
What if someone hacks your 1password account? It's the same exact scenario. Having a single point of failure that one can be extra vigilant with guarding is much better than the alternative of having a hundred unique passwords one must remember.
OR, we should just accept that there's a whole magnitude of difference between sending a password by email on a single occasion, and storing it in plain-text, and focus on the latter problem first.
Who does that? That's even worse than storing it in plain text on the backend.
[1] http://www.assosfactoryoutlet.com/customer/account/create/