I've asked that question so many times, and never got a satisfactory answer.
I have been told the same thing you are saying, but I could never find out if it was true.

There is a new car rental place that everyone is very happy with, but I found that if you add their tax
(different from our car company) and their liability(also different) it ends up more expensive then the company we have been using for years.

If what you said, is true, we have been paying a lot of money for nothing!