A named user migration moves your Adobe licensing from device based or serialized deployment to entitlements tied to individual identities, usually through Adobe admin and your single sign on. Adobe frames it as a compliance and security upgrade, and the technical case is real.
The commercial case is the part Adobe does not volunteer. Migration is the moment your seat count, your product mix, and your discount baseline all get rewritten. If you let Adobe drive it, the new baseline tends to lock in seats you do not use and an uplift you did not need.
Handled from the buyer side, the same migration is the cleanest opportunity you will get to remove shelfware, true down the count, and reset pricing before the new term is signed.