They are ANIMATED bones. MAGIC involved. If you have skeletons – golems(or gargoyles) are not far away. How they move? They have no flesh, no muscles. They do not eat, no drink. They have no brain. Pure magic. For a non magic settings they are really poor choice.
What does make you think that low fantasy equals no magic at all? Fantasy is fantasy, after all.
The zombies. I don’t really mind them much. Thing is that they not fit that much in the settings. Sure they provide a generic enemy but that is all. They are now slow, low damage rather hard to kill enemy but only thing that they have going for them is their reanimation skill. Not mention that I am little tired on zombies(they shouldn’t really be in a medieval setting).
The very same argument could be made for orcs, or vampires, or goblins. Basically anything that is not human.
