What you must bear in mind is that the MPL route is only possible if you are attached to an airline from the outset, and during the multi pilot simulator phase you use their SOPs etc.
That actually requires planning/recruitment on the part of the airline.
Whereas an EASA self funding student, you graduate with a CPL/IR (fATPL) complete the MCC course, and then look for a job.
And of course, not all sponsored airline students go down the MPL route.
They most certainty do more than the minimum MCC course. Probably up to 11 exercises (44 hours) and it can be bespoke depending on the airline.
So unless the airlines decide to plan into at least the medium term, the CPL/IR will continue to flourish. And even if planning does occur, they are not as yet convinced that the MPL route is for them. Cost will be a driver, and unless and until the base training is reduced to the normal 6 take-offs/landings, MPL will not be cheaper.