Because, despite RT's version of events, they are mostly using precision weapons and trying to minimise collateral, plus KSA lack B-52s/B-1Bs and B-2 to blanket Houthi-held areas efficiently.
The US is not engaged there.
It was mostly a UK enterprise, even according to a US news outlet. The Commonwealth fell under the UK back then, and we do acknowledge the massive help from the US. Stalin has the Russian winter to thank for his victory and the D-Day invasions, not to mention the Ruhr valley being flooded.
D-Day: Exploding the myths of the Normandy landings - CNN
It's not actually a bad idea. When you look at Hiroshima and Nagasaki thriving today, one would have to conclude that Islamic theocracies do more long-term damage than nukes.