Not true. Sidearms are used, it is just not the preferred tool for anything other than unique circumstances.
Guys, I promise that I’m trying to rain on anybodies parade nor am I venturing into a discussion that I don’t know something about. I retired as the Division Gunner, 2D Marine Division in 2008, after 34 years of Active Service. I then spent the next four years as the Training Advisor for the CG Regional Command South West Afghanistan, training the Afghan Security Forces. As the Division Gunner, Infantry Weapons Officers, I would rountily have units and Commanding Officers float the idea replacing the M9. It always came back to the same thing, no matter how many studies we did. No one could show where the M9 had ever failed in Combat. Why, because nobody was foolish enough to carry only a pistol in the fight. Yes, I love the M1911A1! But, I do not advocate spending money on a system that meets the current needs. There are only a very few Sepecial Operations units that use a “Back-Up” gun for very technical use. They already have their new gun.