when i was at the big 4 i did get reimbursed for mileage in excess of my normal commute to the office. that is pretty much standard business practice all over the place. i guess you guys view this as a car allowance but they are just reimbursing for your wear and tear and gas on your car for making you drive above and beyond what you normally would to your home office. we got reimbursed for cell phones as well. any parking outside of your home office was reimbursed. we paid for team lunches on the firm/client, etc. if we worked more than 10 hours a day we would get free dinners, at some clients, depending on the budget we would buy dinners regardless.
i guess you guys have a much wider view of a car allowance than i do. to me a car allowance is what goes on your w-2 as income, otherwise you are just get reimbursed for your expenses.
i thought the real savings came from all the meals that were for free. there were months though where i had audits about 40-50 miles from the house where i was making several hundred dollars on top of the free meals. while it helps, i dont know that i would really budget those benefits. id rather be conservative and budget as if i were paying for everything and then have the pick up when you are under budget.