If you only need one animation angle, just draw your object at 0 degrees and as you say, it'll smoothly rotate through 360 degrees. However, there are lots of cases of animations where objects can't be rotated automatically through 360 degrees. As Rich said, pokemon-style grid games use a different image for each of the four directions you can move in. Isometric games use a different animation usually for eight different angles - you absolutely can't let one image rotate through 360 degrees for that!
dustingunn, some of your points are legitimate bugs. If you report them to the bug tracker they can be fixed. While the forums are a good place to discuss things like the purpose of animation angles, they're not very good for bug reports (the tracker is one central collection of all reports so we don't need to search through forums; bugs have open/closed statuses; people can attach files; each bug has its own comment thread; bugs can be assigned to developers; developers can request further information, etc etc).