I have been looking for below-knee cargo shorts that have a gusset. Every short I buy inevitably rips in the crotch, and I feel a gusset would protect against that.
I’ve seen someone in public wearing a gusseted below-knee pair of shorts, and I regret not asking where they got them (though guys don’t typically talk fashion).
A gusset doesn’t protect against damage; it alters the pattern to allow the pants to have a greater range of motion. If they’re tearing out catastrophically before the fabric is worn, then a gusseted design might help. If the material is wearing thin and then failing, then you need a design that has better, more suitable material. (For durability, I prefer cotton-poly or nylon-cotton blends. For extreme durability, there’s also a few kevlar-cotton denims available, but there are no manufacturers I know of using those for shorts.)
FWIW, loose doesn’t actually equate to good range of motion. If you want the best possible range of motion–regardless of material choices–the crotch of your shorts needs to be as high as possible.