Having your odometer connected costs ~$1k/y in depreciation, and people don't generally disconnect it. Do you think they'll start for the opportunity to save an additional $100/y?
Older cars don't depreciate as much. Mine are pretty much done depreciating. I also understand that it is possible to flash the ECU on some newer cars to change the mileage.
I just checked and according to the NHTSA cars over ten years old aren't even required to have a functional odometer (you just have to disclose it when you sell it). I'm not sure how common odometer fraud is, or would be under your proposed law, but the bigger the incentive the more likely I think it would be to occur.
You are right though most people would comply with the law.
