Basically: Sometimes they do, but most of the time they're too stressed. Juveniles that aren't comfortable enough in their surroundings to behave normally. They're also normally massively overstocked in a lfs tank because its a storage unit not a home. This overstocking makes them feel too vulnerable to attack.
Puffers don't eat fish so they don't attack for food but they do like their own space. In a very large tank you could mix a puffer with smaller species, this tank may be ok for them depending on the species of puffer, the personality of the ones you have and the aquascaping. Unfortunately the first sign of trouble is normally shredded fish floating around. :(