I think part of the problem is simpler. You can have a photo line-up of the doctors, as in the publicity images for the 50th. Or you can have one of the actors-who-played-doctors. But you can't have both at the same time, since Peter Cushing was another actor for the first doctor. (Including stage doctors makes things even more complicated). And if you want to emphasise the doctor, not the actors, excluding Peter C is the result.

But because of the same effect, I've always felt McGann is over-emphasised, given that nothing came of his incarnation.