These things come in handy more often than you might think.
Despite the fact that filmmaking is one of the most technologically advanced art forms, there are lots of little problems that remain without solutions. Take for instance leveling and stabilization—sure, there are plenty of tools out there that will help you level your camera and make it steady, but there is by no means a universal solution to this issue. A single dip or bump in the landscape and boom, your shot has a Dutch angle all of a sudden. So, when shooting without a tripod, is there a tool that will let you make small height adjustments to your camera to ensure that it stays level and stable? Yes, and according to the team over at The Film Look it's nothing more than a simple doorstop.
Who doesn't love weird, random solutions to really pervasive, irritating problems? Now, some might say, "Yo, if you put your camera on a tripod you wouldn't have this problem." True, but what if you need to get low to the ground? "Then use a tabletop tripod, idiot." Okay, but what if I don't have one or can't afford one? "Filmmaking's expensive, noob. Deal with it." Okay, hush.
Fact is, sometimes these situations arise. Sometimes you're shooting and just need to boost one side of your camera up a bit or your dolly track or your already full-extended tripod leg or a chair leg. And sometimes, you just need to prop open a door. A doorstop (or door wedge, whatever) seems to be an extremely good way of adding small, incremental amounts of height to things—and they're small—and cheap—so why not have a few lying around on set somewhere just in case?