If one complies with a request such as this, your reputation is driven down because the customer assumes that, after you aided them in cheating the insurance company, you must be cheating the customer too.

I always refuse and indicate annoyance at being asked to do this. Usually, I continue with that customer and I always get recommendations through that customer -- resulting in multiple lifetime customers -- who don't push for similar "services". And, if we don't continue, this is good too, because I now know that the customer will attempt to cheat me whenever possible. I have lots of great customers, I don't need a cheat.