Seatbelt and helmets (for motorcycles and bikes) serves the same purpose to keep the government from having to pay people to scrape your ass off the pavement.
Big picture: collisions are expensive, collisions with fatalities are WOAT. It also slows down traffic considerably. So government has to spend extra money on investigation of a death and citizens have to deal with cripple traffic because your dumb ass can't take 10 seconds to put on a seatbelt or a helmet?
GTFOH.