Your Messages. We do not retain your messages in the ordinary course of providing our Services to you. Once your messages (including your chats, photos, videos, voice messages, files, and share location information) are delivered, they are deleted from our servers. Your messages are stored on your own device. If a message cannot be delivered immediately (for example, if you are offline), we may keep it on our servers for up to 30 days as we try to deliver it. If a message is still undelivered after 30 days, we delete it. To improve performance and deliver media messages more efficiently, such as when many people are sharing a popular photo or video, we may retain that content on our servers for a longer period of time. We also offer end-to-end encryption for our Services, which is on by default, when you and the people with whom you message use a version of our app released after April 2, 2016. End-to-end encryption means that your messages are encrypted to protect against us and third parties from reading them.
If the media messages are e2e encrypted, what is the point of storing popular messages on the server for a longer period?