If your Internet connection is up while you install Windows 8, it will force you to create a Microsoft online account to access your local computer, without giving you much choice to like opt out of this.
In fact, if you choose to create a new account, on the next screen there is a button to skip it. This button should be earlier in the interface, don’t you think? On the other hand, you may just unplug your internet connection while installing Windows 8 to force it set up a local account right away.