Age and years present their challenges too. Teens have acne, grandparents have wrinkles.
However, when capturing family and friends in photographs, we should be happy with the results, shouldn't we? I mean, these are the people we love — warts and all. You wouldn't change a thing about them in real life, so why do it in pictures?
Simple answer I suppose is because we can. While I would never alter an eye colour or smooth out granny's lined but loved, visage, I have, I admit, removed a zit or two and brightened a few teeth. If the means wasn't there I wouldn't consider it. But it is.
Though I adore that relative's slightly imperfect countenance, or see the vanity in altering an image of myself, I can't dismiss the fact that everybody likes to look as good as they can. It's not about a transformation to the unrecognizable, but about creating as flattering a picture as possible. In photographs I can have that sparkling smile I've always wanted.
Not to mention, retouching gives a professional edge to your shots. These websites offer techniques to show you how, and for the novice a handy tool to achieve it:
PSD Retouching Tutorial Healing (Part 1)
PSD Retouching Tutorial Dodge and Burn (Part 2)
Smashing Magazine 70 Beauty Retouching Photoshop Tutorials
Digital Camera World Retouch Photos in 10 Easy Steps
wikiHow Use Photoshop to Retouch Facial Photos in 8 Steps
Photoshop Tutorials Photo Retouching
Makeup.Pho.to Automatic Online Photo Retouching