...because delta knows that if they didn't have that pay then they would unionize and probably be able to negotiate something as good if not better (edit: better than what they want to offer down the road. They beat the union rates so they can point at it and say "I told you so!", discouraging a would-be unionized workforce now so they don't have to negotiate with a union later and can get away with the sort of underhanded shit that a strong union would be able to stand up against, including but not limited to lower wages and poor working conditions.)
Just because there isn't currently a union doesn't mean a corporation like that isn't kept in check by both the realized and potential presence of unions in their industry...
...because delta knows that if they didn't have that pay then they would unionize and probably be able to negotiate something as good if not better (edit: better than what they want to offer down the road. They beat the union rates so they can point at it and say "I told you so!", discouraging a would-be unionized workforce now so they don't have to negotiate with a union later and can get away with the sort of underhanded shit that a strong union would be able to stand up against, including but not limited to lower wages and poor working conditions.)
Just because there isn't currently a union doesn't mean a corporation like that isn't kept in check by both the realized and potential presence of unions in their industry...