You have to understand, any time the politicians can stick it to someone else and appear to be giving a "special deal" to their constituents(read that more votes for me), they will. Take a close look at the fees charged to semi's, RV's with toads, and other large vehicles. Stick it to them personified. Of course they all justify these blatantly unfair toll setups by many different forms of fact twisting, but any time votes and a pool of money that they can tap for their pork barrel is at stake, it'll happen. If I drive over the Bay Bridge (US-50) over the Chesapeake Bay in Maryland with the toad attached it costs me over $10 more than if I separate the vehicles and pay separate tolls. If I had a Maryland tag instead of a Delaware one, my tolls would be considerably cheaper. 
Don't hold your breath for getting this straightened out. It's all about votes and money. Get in the way of a politician with those in sight and you'll get run over for sure.