Pizza hut with 10 waiters and waitresses serving 30 tables

I just do not get why they hire 10 people to do the job of 3. I have seen full house twice there, but 3 waiters and waitresses would still be enough even if every table is full.
One time I've seen 3 assistant managers at once on the top of the 10 cheap labors. They wear uniforms here, different ones.

Although I have to note that, I am not in the U.S. at this very moment. I've been here since last September.