Why do we have to cut dog toenails? What happens to the toenails of wild dogs?

I know this sounds strange, but as I was cleaning my house this morning, I found the sheath of one of my dog’s toenails and got to thinking that they are due to be cut. Then I started wondering what happens to the toenails of wild dogs and wolves who never have a human to trim their nails.

I also thought about primitive humans, but realized they could bite their nails if they got too long. What happens with the toenails of wild dogs?