"But now grubby teen shoes covering in mud or dog poo will be on the bench seat itself so now that lower seats will be constantly filthy."

Exactly. I cannot see the advantage or improvement. We have "anti-bum" spikes welded onto every conceivable horizontal surface in NYC, even street-level window ledges, the top caps of fire hydrants... they're everywhere you look! That's what they should've done - just add spikes to the top edge of the seat back.

This design is still crap, because if you sit on the top edge, you now have no back to lean against.