Depends on what you're what doing. Personally, I don't use them.

I usually prefer just numbers for both - when writing and when reading, but there are some rare exceptions when titles actually add to the story.

In very rare cases, sure. A lot of times it just feels pretentious.

I always try to name my drabbles. It helps me keep them somewhat organized. xD

For me it helps me keep track of what event happens when lol. Like its so much easier for me to remember that x event happened in the chapter titled *insert title* than it is to remember that x event happened in chapter 5.