Because no hash is eternal and it is only a matter of time between it being leaked and it being cracked. How long depends on a lot of stuff (technology, implementation, password quality and, overall, the value of the account).
Salting, specifically only has one function: making rainbow tables useless and difficulting hash analisys, it is the deffinition of buying you time and making the attacker think twice by requiring more resources (ideally enough that it;s not worth trying)
So, if you know that your users creds are compromised, the only logical answer is to reset them. What you did when hashing is buying time. The difference is that if you bought enough there is little change of incidents from the leak. If you didn't it may get messy. And will.
Welp, they have been using devs Google search history to send them some coding challenges + and an interview for a position there for a long while now. (and probably other unspeakable things, who knows)
If your search history matches the developer profile they put together with your data you get abducted and dropped here https://foobar.withgoogle.com/ . Scary.
The amount of data that is sent during the unlock process is absolutely ridiculous. Ever had an environment variable you don't want to share with Xiaomi, together with IP address, mail, phone number, geolocation, serial numbers, etc. ? Because all these gets sent. Unnecessary.