There are 2 benefits of using TOTP here:
If an attacker gains access to your password, maybe through a keylogger or browser extension, the TOTP code will expire after a minute, and the attacker won’t be able to log in later.
Using 2-factor authentication (in general) allows you to keep your login information on 2 separate devices, such as using your computer to store passwords, and your phone to generate TOTP codes. Most people (me included) will probably use 1 device for both though.
(It is possible to scan both of them)