Why didn't Windows Update notify me immediately of the vulnerability. I have automatic updates enabled, why do I have to manually check and install updates. It'

Why didn't Windows Update notify me immediately of the vulnerability. I have automatic updates enabled, why do I have to manually check and install updates. It's dated July 16th, so I was left vulnerable to drive-bys for 4 days. I'm so fed up with Windows and their BS attitude towards security.