They will not get as safe as cars. They are inherently dangerous, it's like taking a car and removing every safety feature. Removing doors, windows and belts. There's a reason that there is a legal requirement in many countries to wear a helmet.

I spent some time in Vietnam back in 2005, after getting a few lifts on the the back of mopeds in both Hanoi and Ho Chi Minh City, I decided to look up some road traffic accident stats for those cities: I never took another lift like that again.