1) Pilot thinks there may be damage/malfunction and does a low pass so that the Tower/Ground Ops staff can have a look. This was evident in a recent one I saw where the pilot had a nose gear fault. It took two passes, but they were able to confirm that the nose gear was NOT down and were still able to have a successful landing.
2) Student pilot either has mechanical issue or in-plane pilot becomes incapacitated. Tower/remote instructor tells student to do multiple low, slow passes at increasingly lower altitudes and speeds to get used to taking the proper heading and control inputs until the final pass is so low/slow that the landing essentially happens naturally.
I'd be flabbergasted if the FAA bans this type of thing, in both of these cases I personally saw (and I'm sure many others), this procedure saved lives. Why would they ban this?