The 3 tyre shops I have used all had them and used them.
At home I use my rattle gun and have never snapped a stud, and never had trouble undoing a nut with the standard + wheel brace.
I've used these torque bars a tension wrench and a wheel brace at tyre shops....I have never trusted a rattle gun alone either at a tyre shop nor at home....At a tyre shop, I don't wish to have a customer complaining they are stuck on the side of the road, with a flat, unable to undo their wheel nuts, or snapping a stud, or worst still, a wheel flying off.
At home, I don't wish to run the risk of snapping a stud on the side of the road undoing the wheel nut, or having my wheel come flying off and smacking some innocient person in the head. So I'll use a wheel brace to check they are tight by undoing them slightly, then tightening them up.
Fair call, not everyone goes to this trouble, but it's something installed into my brain from the time I learnt how to change a wheel