Email already is the single point of failure, password resets. People are already used to looking at their email, account verification etc. People are already used to looking at their email after signing in, 2nd factor with email exists on some sites.

Downsides are that they might be scanned by security software and visited, but surely that's also a problem for verification links? I can't imagine that people would appreciate accounts being automatically verified...

All other reasons I can think of indicate a problem with password resets as well, which also gives access to the account anyway.