I think it must be noted that Ember is growing the market, and has picked up a new customer base. Ive do spot Flix and Citylink and they can still be busy, I'm all for this if we can get more cars off the roads.
I would suggest that the market has grown because of the generosity of the ScoGov bus pass, now extended to under 22s. When introduced it included coaches (which I define as limited stop and generally booked in advance) because throughout the West Highlands these services also provided the only bus service ( stops almost anywhere on request and no pre-booking). Quite reasonable but this is where the law of unintended consequences comes in. Bus pass reimbursements are now being used to support the growth of Intercity coach services.
The under 22s and 60+ population are the major market for public transport because they are less likely to have cars or at least drive long distances and these Intercity operators are exploiting the rules to provide services which are purely coaches with no bus element. I would guess that outwith the tourist season the vast majority of passengers are getting their fare paid by the ScoGov.
At the same time the ScoGov is heavily subsidising train services operating along the same routes*. Given the state of their finances, it makes no sense. Bus passes should only be valid on routes which provide a bus service for a substantial part of their journey.
But given that there's an election next year, I don't expect this nettle to be grasped.
* I know that the coaches and the train take a different routes between Dundee and Aberdeen buf since most coaches run nonstop, it makes no difference.