Likely because commercial fishermen don't care about habitat - if they did they wouldn't be dragging trawls through sensitive ocean habitats, such as cold water coral beds, that take millenia to develop and are destroyed in just a few passes. I don't have the URL but there is a very good article about this on the net. As with all people there are individual exceptions, but in general commercial fishermen are not our allies. Prime example in the Columbia - the Corps wants to restore the WW2 vintage boat basin that was dredged in the intertidal area adjacent to Lois Island (actually the tide flats are now the island), using dredge spoils, to create more intertidal habitat for juvenile salmon and to get rid of dredged material without disposing of it in productive fish habitat. They are being mortally opposed by - you guessed it - commercial gillnetters, because this deep water is easy to fish in. These people are not our freinds - please don't buy thier fish.