Deleting Old Users

We have a ton of old employees whose KLAS accounts remain on our system.  Although they are marked "disabled", I'm wondering if there's a reason not to delete the users from our system?  

There is a reason! KLAS needs a record of the account to continue to show what actions were taken by that account. For example, records of who last checked in an item now found to be obviously damaged, or who assigned an item to a deceased patron. Even in places where the user who completed an action isn't recorded on screen, sometimes that information is logged in a way that we could retrieve it if needed--so long as the user account remains in the system.