A lot of the blame goes directly to the buyer, hasty unresearched choices of fish. But let's not forget that in a lot of cases the sellers need to shoulder some of the blame too.
LFS's, the ones I frequent anyway, seem to be getting better at giving more detail on the info cards attached to the tanks. The staff ask the buyer questions too which is a step in the right direction.
The days of just having a species name and price tag on a tank, and the staff member just handing over fish to a customer without question seem to be a thing of the past.
Sadly though the old practices will still remain in some places.