I think it's just because I carry around a flashlight so I'd just use that.

Let's be honest. What really bothers me, is having less than 50% charge on a cell phone. So when I see people using the flash for sustained periods of time, it makes me cringe. Just a personal pet peeve that does not deserve any real merit.

Plus, if you don't have an actual flashlight, of course you're going to use your phone. Why wouldn't you?