In freshwater, nearly all fish in pet stores are captive bred. So in freshwater, overfishing is not a concern.
Are you sure about this part of your information? I have heard different.
Obviously, most livebearers are going to be captive bred, and the poor breeding of neons and dwarf gouramis is well known, but what of other popular species such as:
clown loaches (difficult to breed in captivity)
many corys (recent shortage due to drought in Amazon- surely that must mean wild caught fish),
cardinals (said to be hardier than neons because wild caught- though this may have changed)
plecos (difficult to breed)
bala sharks (need to be big to breed= expensive)
khuulie loaches (only available seasonally, which again suggests mainly wild caught fish)
Pretty well every lfs stocks fish like these, and I would be very surprised if it really proves more economical to set up big breeding programmes for them rather than send some poor underpaid fisherman out with a net. Even if some of them are possible to breed, and it may happen now and again, most dealers are going to go with the cheapest option.