Missiles have a lot of value. Crashing them expends that value. Governments still crash missiles into their enemies.

Let's go with a proof of stake coin like tron. They have a 2.5 billion market cap. That's more than all of the pentagons ai budget. Congress was bitching about the f35's 94 million dollar price tag. Do you think they are going to vote to give a budget for not only the attack but the person ell and hardware as well? All for a, according to HN apparently, "insignificant financial threat". Doubtful. Easier to just regulate it with a single pen stroke.