The only reason you have regionals in the USA is to fly routes for the majors under contract. That is the only reason most regionals exist. They also don't fly the same equipment either.
It would be like saying the EMB 145 crews doing Denver to Chicago for a regional should get paid the same as 737 driver at a major? A lot of routes simply wouldn't be profitable if you put 180 seat aircraft on them. If they aren't profitable they get dropped.
See the problem?