I think we must/should consider that fishes in the wild school tightly largely out of fear of predation by larger fish.
When they travel this way in tight formation,it makes it a bit harder for larger fish to single out one or two.
In an aquarium where there hopefully is no fear from predator's,the fishes often scatter all over the tank but somtimes school tightly just before light's out for the day in my observation's, and of course they swarm at feeding time.
For fishes that do however seem to stick together more frequently than most,, I would select the rummy nose.
Often see these post's where folk's want tight schooling fish but if given peaceful surrounding's,, the fishes don't need to school in close quarter's and often don't.
Don't we all want peaceful setting for the fishes ??
Well except for cichlid keeper's (whole nother story).
Might also consider that photo's of tightly schooling fishes may be for photo purposes only.Fishes may have been placed in the tank just for that photo and being unsure of their new surrounding's,they stay in tight formation.