This is insanity to anyone but a photographer. I wonder how often it is that a photographer loses out on the proverbial jackpot when a customer resells their images.
If you give a customer digital copies and they "retouch" them or crop them and present it as YOUR work, that's a huge frustration.
Say you shoot portraits of a family and give them the originals. They do a lousy crop of the kids, chopping off the parents' heads and send that out to their friends/family saying that they got the pictures done at Smith & Sons and look at the kids!
Some people will look at that picture and say "Wow, Smith & Sons did an absolutely terrible job, why would they cut off the parents' heads?"
That kind of mis-representation.
Just charge for your time and maybe a reasonable amount for digital copies and be done with it.