Gas milage is better on most scooters, and 2 strokes tend to pollute more than 4. Riding a car or scooter is not a right, but a privilege. You are licensed by the state to operate a vehicle. Because the state issues the license they are some what responsible for insuring the safety of their licensed riders, that's why there are mandatory seatbelt laws, and because they save lives. They same is true for helmets.
I have no illusions that once I throw my leg over the seat of my bike I'm willfully engaged in something dangerous, many more times than driving a car. There are no seat-belts or air bags. It's even more dangerous -- in terms of limiting injury, if you don't wear a helmet. That's why I took a safety class, surf riding forums and want to have the Roadcraft category added to this site.
Their may be upgrades to motorcycle and scooter engines to lower their emissions, and who knows all vehicles may eventually go electrical in the future. What you're suggesting is pretty doubtful -- the government banning scooters because of their emission standards or lack of safety. Scooters are more numerous in Europe and Asian than in the US and there isn't a move to ban them there.
-Wolf