I think you, and damn near every other person on the internet hand wringing about this kind of stuff, vastly, vastly over estimates the conversion rate between

I think you, and damn near every other person on the internet hand wringing about this kind of stuff, vastly, vastly over estimates the conversion rate between "shitty bike with more power than it probably should have breaks something" and "mows down some elderly lady" And you're also over-estimating the number of people who will care when that conversion happens. Because odds are when someone does have a mechanical failure and mow down an elderly lady it will be preceded by a bunch of stupid decisions not having anything to do with that mechanical failure and contrary to what you may believe based on HN/Reddit/Twitter commentary, the general populace is well aware that you can't legislate away stupid. And as others have said, there's a mechanical aptitude bar to entry for using those kits that make them less common than you're implying they are.