True that the password reset and the "login" using this proposal travel the same path and present the same attack vector but there is some disadvantage to the frequency in which the "login" system would travel down this less-than-secure path. The more times you use this the more likely that someone will just happen to be watching and waiting at the right time.

Let's not forget that most of the email system is still not encrypted (last time I checked anyway) even though the last mile between your mail server and your client may be.