In most states, roads are paid for with gas taxes, tolls, vehicle registration fees and other such voluntary fees. Most people who do not drive or use bikes exclusively do not pay any sort of registration fee that goes towards road maintenance.
We pay a ton of money for roads in this country, and all of that money should go strictly for roads and not some BS trail that drivers cannot use. If someone wants a bike path, let them pay for it.
Have you ever heard the phrase “money is fungible”?