I mean most people won't until that day they find out theirs a house in Idaho under their name (and yes I've seen just this happen).
The problem here is because of all these little data leaks you as an individual now bear a cost ensuring that others out there are not using your identity and if it happens you have to clean up the mess by pleading it wasn't you in the first place.
The real kicker is trying to prove which leak your SSN came from. If your SSN gets leaked by 3 different companies, and 6 months later someone uses your identity to commit some crime, you can't have each company share 1/3 of the blame.
Sure. In those cases, there are damages and that creates liability. I'm not sure what damages I've ever faced from any leak of e.g. my SSN.