I get your point; however, in my opinion bike paths are a very unique item limited in use by a certain group of people. Sidewalks, schools, etc. are used by a large majority of people. BUT, in fairness to the issue, I was in San Diego a couple of weeks back and there are bike lanes throughout the city and they seemed to be used by lots of people, so I could very well be off base.
By the same token, airports are used by a tiny minority of people, yet we pour public money into them too. I think we lose sight of the idea of something being a 'public good.' I may not benefit directly from an airport subsidy or spending on public schools, but I like having them. I can travel via air transportation or send and receive goods. And it's in my benefit to see that the public school graduate actually knows how to read the instruction manual when it's time to fix the brakes on my car.
Like the library, bike facilities are a public good and we may use them or not. I had a co-worker who insisted that libraries were a waste of tax money. "They're only wasted if you don't use them," I said. In that same sense, public parks, linear parks, multi use trails and the like are only wasted if we don't use them.
While I'm not a proponent of bike lanes, I do understand their appeal. (They're still the subject of this thread, after all.) I have misgivings about setting aside public space for the exclusive use of one group of road users. And I don't tolerate the fear mongering that some bikeways advocates rely upon. As responsible citizens, we cyclists should insist that public monies spent on our behalf have genuine, measurable safety benefits. Too often, bike facilities and even bike laws are little more than feel good approaches or window dressing. In even more cases, facilities are poorly designed and ill maintained.