Unfortunately, the American population has decided that it won't ride on turboprops (and also won't pay an airline fare that covers it's own costs) and therefore the "50s" are here to stay for quite a while. While I agree that "50's" have no right to be flying many routes that are currently served, they are also the exclusive airline server of several communities.

Until people are willing to buck up and fly turboprops (sadly, unlikely), 50's will dominate this niche market.