Government officials want more money for random nonsense and corruption. Voters disapprove. Government officials pick something to hold hostage, such as the library. They propose a special library tax. Meanwhile, the random nonsense and corruption is getting funded.

The voters aren't that dumb. They know the library could be funded, and they don't wish to fund random nonsense and corruption.

It's a threat, "Give more money or we'll cut something you like!", when the voters can plainly see that funds are going to things that are improper.

Suppose the voters fund the library. Next year, when that funding gets diverted, the government will come asking for more. Maybe it will be a different thing needlessly on the chopping block.