Why is it called a haircut? Most people get hairs cut from their head...not just one hair.
Do you like my hairdo? How does my hair look? I'm going to pull my hair up in a ponytail.
Why not hairs?
Your hair is all over the bathroom floor! Pick out your long hair in the sink, gross!
Again, why not hairs??
People do say: I have a few stubborn hairs here.
But they don't say: I just got my hairS cut.
Well, I got my hairS cut last Thursday.
There you have it. I love you Wikipedia. But I also like saying "I just got my hairs cut."
Especially when I say it with a hillbilly twang. Yee haw!