The scrollbars are not created by Access. Instead, Access uses standard Windows commands to create a window. As such, scroll bars and the minimize, restore, close buttons in upper right on title bar are created by Windows. This means that the theme on Windows itself governs the creation of all window controls. (Not controls INSIDE the window, but controls ON the window.)
Believe it or not, this is a GOOD thing. Otherwise, you'd have a myriad of programs "rolling their own" window formats and your users would quickly get SO confused. Because while you HAVE to hate Windows for a lot of things, ... at least it is consistent in the mistakes it makes and the ugly things it creates. It is equally as mistake-prone EVERYWHERE. After a while, you sort of get used to it.