The reason seems simple - it's easier to sell more if you're well known. People will buy simply due to endorsement. It's also easier to attract a compatible customer base when people can see you. That might be LESS important if a key part of your business doesn't involve direct interaction with clients/customers... but still.
Even if someone's business DOESN'T require this element for success, I almost always recommend they pursue it - even if it's just to be "famous" to their peers and colleagues (and competitors) if not to the public. I think it's one of those things where it's easy to do, and the benefits FAR outweigh the detriments.
But I know some people don't want to be even mildly famous... or some people are scared to... or some people just don't know how to do it all. I know a lot of people here trade under their own name, but a lot more don't. And for some that do use their own name here, it doesn't mean they stand at the front of their business necessarily, either.
So what do you think? Is fame necessary? Is it desirable? Is it difficult? Is it worth it?