There's a difference between those two features. Changing the password requires entering the old password and entering the new password, so you're authenticating them via their password. Resetting the password requires sending a link to an email account you know they own, so you're authenticating them via their email account.
It's SORT of a "thing you know" vs. "thing you have", except the email account is kind of also a thing you know.
Huh, I was just thinking about this the other day, and wanted to rant about it but never got around to doing so. It's extremely annoying when I land on a login page from an email when I clicked to take a specific action. ESPECIALLY when logging in takes me to the home page, and not even to my intended destination.
It's SORT of a "thing you know" vs. "thing you have", except the email account is kind of also a thing you know.