Dress and comportment are important for men and women in careers and in regular life. The "suit does not make the man," but dressing right for the occasion matters a lot to other people. First impressions are everything. Of course, you have to have more to offer than your presentation, but it matters all along the way until you have fulfilled your dreams. Then you can do whatever the heck you you want. Flip flops and t-shirt, Unless you are in the rag trade.
If you look and behave like a professional, you can become one. Assuming some cleverness and, like the car below, attractiveness isn't enuf but it's a good start. Easy things for a career: Fitness, good clothing, agreeable attitude, even if fake.
Addendum: Scott Adams says good shoes are the most important part. Maybe, but good hair might be equally so.
For the ladies, Nora Gardner - Wardrobe Panic Eliminated