One reason not to trust TLS is that it's one system that you want to be secure for all your users - indefinitely. If in the future there was some method to crack the TLS or the appropriate keys/certs were leaked, any recorded traffic could be retroactively cracked.

Remember also it wasn't so long ago we were talking about things such as POODLE attacks. For all we know, some bad implementation of TLS 1.3 could default to some crappy easy to crack algorithm.

I believe there was a paper (can't find it now) that speculated about the cost to crack a specific TLS setup to be about $10 million USD in processing, going back some years. (I think it was in reference to some half of VPN traffic at the time using the same keys.) If Moore's law still applies in any sense, that cost likely halves every two years and people only really change their passwords if they have to.

Another reason is that it reduces risk server side if you are never handling user passwords - at worst an attacker gets a temporary hash that's valid for a short time, specific to that server. Maybe they can do some harm during that time, but you can ultimately revoke that key and undo the changes to the user's accounts.