Accountability and folks being able to find/recognize my stuff also plays a huge part. I do use a seperate name on a sub-genre of what I do, because it's more of a niche market, and different from my more "standard" work. But those knives also have my real name attached to them. I feel this builds a certain level of what-you-see-is-what-you-get among my clients; they're not dealing with a corporation or an answering service or a salesman, they're dealing with me.
Honestly, it's mostly pride. I don't need to hide behind some made-up marketing-guru focus-group-driven trendy name.