If someone hacks into your email account, they can just trawl through the email archive and harvest passwords from past password reminder emails. With a temporary reset token, they have to initiate a password reset request, which you should notice: (a) you might notice the email if you have e.g. push notifications enabled, or if the attacker doesn't delete it quickly enough, and (b) your real password will suddenly stop working.

Additionally, even if your reset request is harvested via MITM, if you use a single-use reset token, and an attacker uses it before you can, you know something is up. Even if it's not single-use, your password suddenly no longer working should ring alarm bells.