Because AI art is shit at this kind of thing. Not incapable of, just absurdly fiddly to get obedience from. It'll get you 75% of the way there, and then you actually need to know how to edit an image, which is where it lets you down.

Go ahead and try generating images of a family during benediction wearing ear bandages and you'll find it really struggles with getting that last part right because it's not typical subject matter.