Car companies don’t certify their own safety, they have to send them in to the government to be crash tested. Car deaths don’t happen (much) because of mechanical failures, they happen because of crashes. They don’t self-certify their crashworthiness.
Most people don’t live somewhere where there’s a subway to the airport in the USA. You can count on one hand (and probably have multiple fingers left over) the number of cities where you have that option. For most people a bus adds significant time to their trip. I can take a 30 minute Uber whenever I want or a God-only-knows-how-long bus ride. Even if it weren’t for the mentally ill (but mostly harmless) passengers, a taxi is in every way a better experience than a bus, and still negligible risk, it just costs more.
Even if we could abolish the second amendment that still leaves over 300 million guns here, and this may surprise you but people also sell things illegally. The problem isn’t the law, it’s that people want guns.