Like Poolie said, most people don't and won't exercise so it's a waste of money to spend billions doing something that only 1% of the population would ever use. I ride the bike paths in my town and on occasion I run into another cyclist, but for the most part their semi deserted. The only busy part of the paths is the part where a popular park is and people are either walking the path or riding around in circles around the park, but the path network is about 30 miles more then just around the park, and once you get outside the park I may run into a couple of dozen riders along the 30 mile stretch.
I use to live in California and Bakersfield had about 60 miles of paths, and again, except where there was major popular park, most of the path was lightly traveled, granted more traveled then here in Fort Wayne Indiana, but still not used enough to justify the millions of dollars it cost to put the path in! I did live in Santa Barbara CA and those paths were will traveled for the most part, but it is a college town, it's a tourist town, it's along the coast, and people who live there like to get out, and a lot of people ride the paths simply because housing is so expensive it leaves very little money to own a car or own a decent one for a lot of people so their almost forced to use the paths. But a town like Santa Barbara would see more use of paths so in those areas I could understand, but for other areas I have a difficult time with the expense.
I've run into this argument before that I think it's a waste of taxpayers moneys to built these paths for such low amount of usage, I think cyclists would be better served if we just had separate lanes marked on regular existing roads, and it would be cheaper thus more lanes could be put in. The average separate bike path cost about a million dollars a mile to construct, the average bike lane cost an average of $23,000 a mile; so guess which one I think would be more suitable? Most cyclists I ever talked to vehemently disagree with my position, that's ok, it's just an opinion. But with communities already on the edge of financial collapse it seems unwise to have projects like that...as well as other wasteful projects. All these wasteful projects do is force the communities to raise property taxes and sales taxes to cover these expenses which straps homeowners and renters with the increase costs of higher taxes. Of course communities get federal grants for these projects, but grants still come from taxpayers.