Nope, you're not missing anything. Per the Online Help doc, the Traffic To Views data is only retained for up to 30 days. I believe this limitation is in place to maintain performance for all Tableau Online users due to the large amount of data needed to provide these statistics.
This is true -- currently we only retain data for 30 days. We are working on an updates and improvements to admin views that we plan to ship in the next few months. We an update this thread when we had more details. Please feel free to provide more information about your use cases for this data to help guide our designs!