Your face is the first thing people notice about you when you go out into the world. Quite rightly, most of us put a lot of effort into making our faces look clean, healthy, and happy much of the time. Some people even go so far as to think of their faces as masks which they can use to alternately hide or reveal their true feelings to the world as each situation requires.
When you roleplay, your character is the mask you wear in a world where your real face doesn't matter at all - it defines who you are within this fantasy world and it determines how others will react to you as one of its denizens. Likewise, it deserves its proper amount of attention, like the care you give your outward appearance for your real life interactions. The method of caring for it is different of course, but the spirit and intention is the same.
Roleplayers have certain conventions you can use to quickly identify yourself as one interested in interacting with them. But more important than these is your attitude: just as the way you stand, smile, or keep yourself clean are all more important than the actual look of your face in real life; so, in roleplaying, a humble manner, a friendly approach, and a confident integrity are all essentials, whereas things like race, class, funny quirks and accents are all merely supporting elements.