Have you ever seen anyone lean against a door frame and scratch against it? That's what cows look like.
When I was visiting Triple H Farms, I saw their Lely cow brush. The theory is that since cows want to scratch themselves, you might as well make it easier for them. Lely's marketing material says that good cow comfort results in a "healthier and more productive herd."
This is an automatic brush. When they touch it, it turns on. It looks like a big car washer brush:
I watched as the cows left the robot milker and took their turn with the brush. They obviously enjoyed it.
On the streets of San Jose in Costa Rica there were several men selling back scratchers. They just had them fanned out in front of them, hawking them.
That is, I assume they were selling them. Maybe if you walked close, they'd just scratch your back. Resulting in a healthier, and more productive crowd!