You’re right, otherwise we’d all be powering our cars with with zero point energy reactors.
Clearly feasibility has a big part to play as well and everyone driving around little fission reactors would be ridiculously impractical from both an engineering standpoint, as well as a safety one too. Not to mention it becoming a terrorists wet dream because of all the waste material. (Not that I’m normally one to play the “terrorist” card)
Terrorists currently utilize cars for destructive acts all the time - it hasn't caused us to abandon them.
I wouldn't be surprised if, had we gone down that path, automobiles had less fissile material in them than platinum. Currently fissile materials and high explosives are purchasable, we just keep an eye on purchases and follow up on suspicious buying patterns.
Clearly feasibility has a big part to play as well and everyone driving around little fission reactors would be ridiculously impractical from both an engineering standpoint, as well as a safety one too. Not to mention it becoming a terrorists wet dream because of all the waste material. (Not that I’m normally one to play the “terrorist” card)