Attackers generally aren't targeting a specific individual, they got a dump of X million passwords from some compromised website. Being able to connect those directly to working accounts rather than having to burn IPs and get them rate limited and/or banned trying duds _is_ valuable information.

If you have some attacker after specifically you, yes this information is of less use to them, because they will have tried every password of yours they have on every website already hoping you reuse passwords.