From a totally nutritional perspective yes there is no 'need', but even captive bred fish will have an in bred need to predate.. My captive bred fahaka hunts and burys herself in the sand. No one 'taught' her to do that, she has an inate desire to. Dempseys are still predators and will have the desire to hunt.
If you were in a house with 3 square meals a day but nothing to do you would go nuts If someone gave you an Xbox! Lol
It's about mental enrichment as much as nutritional.
I don't have any proof or can point to any study. I like feeding live foods because I don't think pellets can replicate the nutritional value of whole body live foods. Some people like to feed live food for the bacteria, kind of like a probiotic. Which makes sense. I feed clams, mussels, crabs, worms and fish. Algae and plants for herbivores. I will feed live once or twice a week.