I would say, because of the location of the pilot and the burner and the inability to easily "see" what is happening, in the case of the grill lighter. You have to consider the apptitude of some of the users, as well, I think.
What Rene described as his process is a very good example. The OP has difficulty getting down there to light the pilot/oven, so if he had an igniter installed, he may still have difficulty observing the status of the pilot/oven burner.
It's just the way I see it as a possible problem, that's all.