Sheldon Brown says that 3/32" is actually better, something about bushings...

Most people are stuck with 3/32" chainrings. It just so happens it doesn't really matter much if you're using 3/32" rings and cogs with a 1/8" chain. Shimano BMX freewheels actually come in 3/32" and say they can be used with either chain, right on the box.