the basic rule is to wear a "right dress to a right time (and place)." a salesperson for instance may have differnt way of dressing themselves with respect to the type or class of products they are offering. Of course, it would be inappropriate for a car salesperson to wear a plain shirt and pants, don't you think so? :)

What's 'decent' is really very relative. Somebody that promotes a beer brand in a pub will certainly need another dress from somebody that works at a funeral parlor. What's appropriate is therefore very relative too. It's not just depending on the company or product, it also depends on the target customer group.

Smart clothing makes someone seem more professional, reliable and perhaps even trustworty. I probably would be less inclined to use a lawyer that turned up to a meeting wearing a tracksuit. And I think most people would have less respect for their politicians if they all slopped around in tshirt and jeans. Also, wearing smart clothes shows respect for the other person, such as when you go to a wedding or funeral.

Every company has an acceptable clothing policy unless they require employees to wear a uniform with the company's logo.