Why is Morph not considered an ability?
The face down morph cards don't have an ability whose effect turns the card face-up. Instead, the rules allow you to turn them face-up.


  702.36d If you have priority, you may turn a face-down permanent you control face up. This is a special action; it doesn’t use the stack (see rule 115). To do this, show all players what the permanent’s morph cost would be if it were face up, pay that cost, then turn the permanent face up. (If the permanent wouldn’t have a morph cost if it were face up, it can’t be turned face up this way.) The morph effect on it ends, and it regains its normal characteristics. Any abilities relating to the permanent entering the battlefield don’t trigger when it’s turned face up and don’t have any effect, because the permanent has already entered the battlefield.