If you take Delta for example, they take out the RJ feed not only because they are unprofitable, but because of the lack of revenue they bring to the table.

Delta wants their RJ with business class section, because they bring a higher revenue, and people are beginning to realize how small those RJs are. When you can get a used MD90 on the used market for about 10mil, it really doesn't make sense to invest in these shiny 200 where it burns more gas/pax, and bring in less revenue per flight.