An oil drain valve is a device that replaces your regular drain bolt and makes an oil change a much cleaner job. When it's time for an oil change, you simply attach a hose to the oil drain valve, open the valve and everything drains cleanly.
https://www.youtube.com/watch?v=eaaT5a13xY8 (note: I am in no way affiliated with this brand or anything. It's just a good demonstration).
Admittedly, for a professional, it probably doesn't really matter that much, but for an amateur just maintaining their own car, it's quite a handy tool. You don't really need to jack up your car anymore, you can't overthread (no need for a torque wrench) and everything is clean.
My question is simple: why aren't these more commonly used? It doesn't look particularly expensive, and it makes the job a whole lot easier. Are there any disadvantages?