Incredibly handy to have. I use them on every bag especially when traveling. If I have something extra that I don’t have space for in my main backpack I attach it to the outside of my pack.
If the kids call it quits and don’t want to carry their little backpacks any longer, it gets attached to my bag.
I also use these to attach the stroller to my backpack when I’m in a area where I can’t push the stroller and keep hold of both of my kids at the same time, like a subway.