In reply to Ryan Hellyer.

Your avatar and author info in a sidebar isn't something available in WP by default. It's a custom feature, your own customization. Most of the users will not have it, and removing author info below the post will completely hide any information about the author, relying only on the 'about' page which, again, isn't available right out of the box. The same applies to single-author blogs. It's not only a design decision, it's common sense. Besides, author block below the post is, actually, a well-recognized pattern, even on single-author blogs.