You can go online and see what people are actually willing to pay for older, low-mileage cars. It's not much of a premium over similar cars with typical mileage. You can't really blame insurance companies when the valuations are determined by what people are actually paying for used vehicles. Sure, you might do an impeccable job of maintaining your car, but a future buyer has to go off of a mechanic's assessment, plus they won't have a manufacturer warranty to fall back on. There's also the issue that newer models generally have better fuel economy, more safety features, etc. Cars have actually gotten cheaper over time after accounting for new features and reliability improvements, which puts additional downwards pressure on the price of used vehicles.
> Currently, the IRS mileage rates for business is $.70/mile, do any of the gig economies pay this? [1]
I used to get paid that rate at my old job and it was an amazing deal, it was way over my actual costs for the vehicle. With a small fuel-efficient car I was covering my gas, insurance, and depreciation with a few trips each year. It was effectively my work paying for a free car I'd get to use the rest of the time.
That's the issue with using one number as a very rough estimate, it has to account for everything from contractors driving work trucks to someone commuting in a Model 3.