Basically, it goes like this: If someone else is playing an elf, I probably make fun of them for being sissies. If no one is playing an elf (or only one of my friends in particular), I will usually play an elf, and I/we will make fun of them for all the elfy abilities they lack. So, while not 100% necessary to a group, they can add in some unintentional comedy, and are a good rounding-out of races.
