> Do the air bags in your car go off at random while you're in traffic?

https://www.nhtsa.gov/air-bags/deadly-air-bag-replacements

"After the air bags were replaced and the vehicle was involved in a crash, the air bag inflators malfunctioned and ruptured, sending large metal fragments into drivers’ chests, necks, eyes and faces, leading to death or severe injury."

So yes, safety features sometimes have flaws.

> If not, then why do you think a system using these jets to avoid accidents would?

For starters, airbags are reactive to an impact, not predictive in anticipation of it.

"We're going to crash" is harder to assess than "hey a crumple sensor in the front bumper just got wiped out".

(The airbag is also deeply unlikely to obliterate a different car, pedestrian, or bike during deployment. They're simply not comparable to a rocket engine on the outside of the car!)