IME the service on RJs is often more energetic and proactive because the crews are usually younger and less jaded. Of course, it's not completely about age. The best service I ever had was from a senior crew on a TATL ex-MSP.

My point is that for the mainline crews who do lots of domestic turns, the motivation to provide excellent service isn't very strong. They already have their job, and are just running out the clock until they can move to all long-haul flying.