According to this article, Microsoft will no longer issue security updates to Windows 8.1 if you don't install the update path.
Since Microsoft wants to ensure that customers benefit from the best support and servicing experience and to coordinate and simplify servicing across both Windows Server 2012 R2, Windows 8.1 RT and Windows 8.1, this update will be considered a new servicing/support baseline... beginning with the May Patch Tuesday, Windows 8.1 user's devices without the update installed will no longer receive security updates. This means that Windows 8.1 users - starting patch Tuesday in May 2014 and beyond - will require this update to be installed. If the Windows 8.1 Update is not installed, those newer updates will be considered "not applicable."
Is Microsoft attempting to drive away all it's customer base? Seems so.