Often gas taxes/vehicle property tax is tagged by the state to be dedicated solely towards road development and upkeep. If there's ever a shortfall, they stop maintaining lesser used roads because the rest of the budget has already been decided.
This is despite the fact that it takes more than gas + property tax to fund the highway system.
Thinking about that... I get your point, non-drivers are funding the roadway system as much as drivers are.
I think its the way that gas taxes for instance are leveraged in the decision making process that makes people think that it makes the lion share of the contribution. When the proceeeds from gas tax falls, lawmakers think less people are driving thus less maintenance is needed.
Not quite zero, there are some speed bumps that I notice in NYC where the bouncing motion of the bikes has worn additional bumps in the speed bump.
Of course, you don't really need the speed bumps in the bike lane. I assume it's there because people will drive around it if it doesn't cover the entire road surface. (Protected bike lanes would fix that, but I'm not really a protected bike lane proponent, so we'll pretend I didn't mention that.)
Sadly, that's not how taxes work. Each tax isn't "for" something, they all go to into the budget and are used to buy stuff.
Toll roads might be a fair example. Those are mostly closed to bicycles.