For me, but it's on so many levels: at work I wear professional clothes so that my clients and colleagues will judge me as serious about my work - I make an effort in how I look, so hopefully they will then assume I will make an effort in my work (which of course, I do!). I also try to stick to the tenet of wear the clothes for the job you want, not the job you do.
Outside of work I want to be judged as fairly up to date, able to dress myself in a flattering way to make the most of how I look. Receiving compliments from others is a massive ego boost, and makes me want to work harder to get more.
For me clothes plays a big part, but so does keeping in shape, exercising regularly, eating well. And I would never post a bikini shot of me on FB so a very old ex would see how well I've aged. Never. Nope, not me.