Probably because you’ve started from a different “something” that is being reduced. Namely, the right codified in the 2nd amendment isn’t about levels of firepower (see SCOTUS in Caetano) so this type of comparison is irrelevant when it comes to the scope of the right.
You indicated that recognition presumes the costs are worth the benefits. I’m not sure I agree with that, but you seem to be confident that when evaluating the costs vs. the benefits, the analysis is clear. But if you only look at one side of the equation, then it’s at best premature to draw conclusions.
Willful ignorance is too.