Yes there is! Great you have a strong, randomly generated password. There’s no collateral damage (you’re having your password manager generate the passwords right?) So your other accounts are safe, you only have to rotate one password.

Well what happens for instance if someone really wanted access to your account? Say it’s a bank, a social media account, or maybe it’s just a game account for an MMO that’s super high value, you have a long and strong password, but let’s say the service’s security wasn’t quite up to snuff or you got phished and gave your password by accident (these things happen, it’s not your fault).

This is where 2FA comes in, if someone manages to break your password the attacker needs your phone, your security key, your fingerprint, etc… To prove to the service they’re you. By having 2FA on the account you’re increasing your defense in depth for your account. If you didn’t have it your account is as good as gone as soon as an attacker cracks or gets your password.

It acts as a second lock that needs to be picked in order to take over your account.

I personally add 2FA to all of my accounts I can, the highest security ones get added to my hardware token. The ones I don’t need as high security go into my password manager (which has 2FA enabled but only available via my hardware key).

Additionally as often as possible I try to use a unique email address for each service (simplelogin, addy.io, or similar, + based email addresses are easily bypassed) they all forward to my email but now you have to guess my email for the service (my own private domains, so not shared with anyone else) and what mailbox it ends up in. As a bonus you can disable emails that are sending spam or see who got breached based on the email.

Again defense in depth, a long secure password is great but that’s only relying on a single lock. By having 2FA you’re doubling your security so to speak by requiring that extra key in order to access your accounts.