Unless there’s an electrical outage during a big snowstorm or heat wave, and then lack of insulation can kill you. Maybe. Or the old people you sell your house to later.

But sometimes you are correct. Like in writing where it’s best to know the rules of grammar before you start breaking them, it’s best to know why the building codes exist before you break them as a DIYer.

Poster seemed most upset specifically about the electrical issues. Those kind of things absolutely can kill you (or the next homeowner), or start a fire that can kill you, or your neighbors.