Because Iran's cyber capabilities are pretty advanced, and the U.S.'s power grid is catastrophically outdated and vulnerable.
A succesful cyberattack against U.S. infrastructure has the potential to result in far more death than any nuclear attack Iran could be capable of.
North Korea is guilty of exactly the same threats, and actually has detonated nuclear weapons. When are we going to start dropping bombs on them?
Not to mention Iran's allies include Russia and China, both countries that we have been deferential to for various reasons until recently.
Something major just happened behind the scenes. My guess is that Israel has uncovered some major intelligence during their searches and interrogations related to Gaza, prompting immediate action. Now, whether that evidence was fabricated or overblown remains to be seen.