Humans are insane.
Case and point - there were FULL PLANS to make a TANK driven with #nuclear power...
...Something that is meant to get shot at, and gets blown up no matter how much armor you give it as humans are SPECTACULAR at figuring out ways to blow stuff up.
Someone had to go "hey guys, maybe radioactive material getting scattered everywhere by explosions, or irradiated tank crews are really bad ideas," as radiation shielding was also an issue.