I mean, it's certainly spooky that the bones are moving when it shouldn't physically be possible, and maybe there's powerful magic reinforcing it, or... Something? It seems like the amount of magic needed to make them the least bit effective could be better used.
One might ask "how can you possibly know how much 'magic' it would require in a general sense?" I'm going by the rule of thumb of "how much is magic being expected to do?"
In the case of a skeleton that moves on its own and is a viable combat threat, I'm considering that magic would have to hold the skeleton together, move it around, provide any of that reinforcement I mentioned, provide whatever senses are required for the skeleton to function, and who knows how much magical nonsense just to get a "nyeh" sound out of them.
Also, I just did a search, and bones are supposedly 15% of a person's total body weight. That might help reduce the magic cost (a bit, still a bunch of moving parts to hold together), but weight matters in combat. Even if someone started out 300 lbs (136 kg) of mostly muscle, that would maybe get you a 45 lbs (20.4 kg) combatant of, well, no muscle.