I’ve seen people wear gaiters in heavy snow and in a marsh. That makes sense, but do people use them to keep sticks and rocks from falling into your shoes?
Depending on the style (weight of fabric and height) they can be quite hot. Personally, I wear them to keep snow out and that’s really it. In northern New England that can be any time from October to June! They certainly keep other small annoying debris out but for me, it isn’t worth how hot they keep my feet, ankles and shins. I would consider them if I was hiking in the dessert simply because I don’t appreciate sand
I have used lightweight/breathable gaiters in the desert, they help keep sand and rocks out.
The waterproof ones are nice to have after a rain shower if you’re hiking in an area with lots of tall grass or bushes; helps keep your pants and socks from getting wet from the residual moisture. Wet socks = wet feet and that is miserable.
I don’t use them for too many snow sports since most of my winter pants have built in gaiters that work pretty well, but for fat biking they are great. Keeps pants from catching on the bike as well as keeping out the snow when I inevitably lose momentum and fall off the trail. My trail craters are amazing.