Regional "Airlines" = Actual Airlines "B-scale" pilots.
It's really that simple. Except they're really more like "C" or "D" scale pilots, depending on the regional in question.
Seemed like a good idea at the time. Pre 9/11, it certainly helped major airline pilots trade scope for other goodies, and I don't begrudge them their right to make this choice at the time. Assuming it WAS a choice, and not just an inevitable consequence of de-regulation which forced legacies to compete with upstarts with much lower costs.
Over the long haul, it's increasingly looking like it was a strategic mistake for pilots overall.