It was to a certain extent, because you needed an alternating PPC , which was always somewhat of a planning stumbling block.
Basically the reason why most actual 78 operators don't opt for MFF, is that the fleet is still too small. With an eventual order from EK, the 78 numbers would warrant for the MFF purchase, because hearing through the grapevine, the 78/77 MFF would not have this PPC restriction.