As someone with large hips and a much smaller waist, I've always got the dreaded "gap at the back of the waist" issue with jeans. Larger hips also mean that my jeans stretch out quicker, which leads to them sliding down a couple days after they've been washed.
Belts only make the gaping at the back of my jeans worse and I find them pretty uncomfortable, so I wanted a different solution.
While brainstorming, I remembered a product I bought a few years ago from Bristols 6 called the Adjust-A-Button
and knew I wanted something like that again. They were really handy, but they'd only last a few months before they'd get bent and start falling off.
This solution is cheaper and solves all sorts of issues:
second and third wear jean stretch
expanding the waist line to deal with weight gain
bringing jeans in when you lose weight and you're in-between sizes
correcting/lessening waist gaps