I am considering a switch to SIXT instead of National as I'm fed up of the risk of getting Volvo's on LCAR reservations, but I was surprised to find when looking at prices that although price is comparable to the competition, if I rent from LAX I can't take the car to Utah or Colorado though I could take it all the way to Washington which isn't really any closer! Oddly if I rent from LAS instead I can get a bit further and Utah is allowed.

Is this really the case? I've never rented a vehicle with restrictions like this before.

It really seems to make little sense - it can't be a coverage thing because Sixt will allow cars rented in Arizona to be driven in:

California
Colorado
Utah
New Mexico
Nevada

So if I was able to get to Arizona I could rent a car which would cover the states I want, including California, but if I rent from the same firm in California, I can't take it to Colorado?