Not true. Offline hacking is not only a concern for passwords used on multiple sites. There are many scenarios where an attacker might be able to grab the hash

Not true. Offline hacking is not only a concern for passwords used on multiple sites. There are many scenarios where an attacker might be able to grab the hashes, but still need to crack them in order to get access to other data from your account. If there is a sql injection vulnerability in the authentication service, for example, it does not mean they can necessarily overwrite the hash or access data in other parts of the application. I once found a bug in a payment processor that let me download the user record including password hash for all users in that payment processor. But I couldn't use that to get their stored credit card numbers directly. However, if I had brute forced those hashes, I would have been able to log in as them and access their other account data and make transfers, etc. I am sure a large majority of those password would have been very easy to crack. If I was an attacker, those would have been my first targets.