The issue isn't standing to "know why". It's standing to sue in court. The taxpayers act through their votes. To sue in court you have to have some specific interest in the issue. It's a standard legal principle and is perfectly logical. Without it anyone could take anyone else to trial over anything.
By the way, are you familiar with the Barnes Foundation art collection in Merion, PA? “No standing” was used in that case as well. Disgusting.