Does anyone insure their modifications on their cars?

they offered him a certain amount… he thought that was low. He had an adjuster come out to assess the damage. The adjuster assessed the damage, and his insurance company cut a check… If you can get it fixed for cheaper than what the ins. company gives you, I fail to see how this makes insurance rates higher… The only difference is some of the check went into his pocket instead of some body shop’s pocket.