Do you even know what a scope clause is?
Yes I do. Anyone who knows anything about airlines knows what a scope clause is. Anyone who knows anything about union contracts knows what a scope clause is. Anyone who actually asks that question has likely only recently learned what a scope clause is.
You look at a scope clause as job protection but airlines see it as another obstruction to flexibility. I can certainly see why they would rather not have one.
Air Canada fairly recently joined a couple of other airlines in the world who have actually forced an aircraft maker to conjure up a special model number for an airplane to embed their scope clause. The CRJ-705 is just a 900 limited to 70 passengers.
Same reason the CRJ-44 was invented. The airlines that operated them had to spend a lot of time, effort and money to "un-44" their aircraft as the scope clause crept up to 50.
I find it amazing that unions have that much clout. All the way to the type certificate of an airplane to impose an artificial passenger limit.