Bank anglers have access to columbia springers. The thing is the average boat is fishing for 1 or 2 fish a day. Whether it be because he can only fish weekends when crowded conditions exist or he is not as good a fisherman. A longer season allows him to make multiple trips and hopefully harvest a few fish. If I'm not mistakin extending the season will also benefit guides.
With large amounts of willing clients why would a guide not want to do everything to make his season longer.