Some feel that the net slows them down. While it may bring the fish into the boat quickly, sometimes the partner is not ready with the net in time or hooks get tangled in the netting. Even the best of nets still get hooks caught sometimes.
Personally, I don't ever use a net for bass as I have no trouble landing them without and I get things done faster without it.
But for anything else (pike, carp, catfish, trout), the net is always handy!