Maybe all those orders will simply replace the 50 seaters ExpressJet and SkyWest have for no real net gain in flying. The two airlines have a combined 486 50-seat jets. To maintain the same capacity on larger CRJ's/ERJ's/MRJ's, you'd need about 320 76-seat aircraft. No surprise then that SkyWest has ~300 orders (plus a whole bunch of options).