Tax time in Americaland--veinglory

I will freely admit that in this post I speak from ignorance. What I know about tax could be written in the back of a stamp--so I would be interested in your thoughts.
First, there are several ways to declare royalties. In the US I think there are two main options: self-employed income or royalties. I am curious which method most people use and why. I declare royalties because I simply don't have the kind of expenses to write off to make self-employment a better deal--also I just can't be bothered with the paperwork.
Secondly, most small businesses offer an option of withholding some portion of income and paying it straight to the tax man, to avoid the worker owing tax in one lump sum. Does anyone know why most epublishers not only do not, but will not do this? Is it just because it would be a logistical nightmare or something to do with publishing as a business?
On the up side, despite writing nothing in the last six month and very little over the last year I still managed to clear just over $5000 in taxable royalties. Not too bad I guess, given that it is largely off backlist. But I really need to get off my butt and write more.