The removal of the Detroit-Pittsburgh service seems more of an indication of the partial failure of the Pittsburgh hub. The Wikipedia article on Megabus notes that 3 of the 7 original Pittsburgh routes were dropped in 2012. The removal of those routes [[and service cutbacks) made it impossible to connect in Pittsburgh without staying there overnight. The number of buses to Detroit was cut at that time as well. Although they did not sell tickets to connect, I had friends go from Detroit to both New York and Toronto through the Pittsburgh hub in 2011, by buying individual segments.
After the Detroit cut, the Pittsburgh ¨hub¨ only has service to DC, NYC and Philadelphia.

It should be noted that Megabus has expanded recently with service from New York to Chicago without a change of buses [[and stops only in Toledo, Cleveland and State College PA). They also now have service from Cleveland to Atlanta with no change of buses.