Chatter feed does not show all updates made by other Users

Please review this article: Chatter Feeds Overview

On the Home tab, you can see your updates, status updates posted by people you follow, and updates to records you follow.

• If you're following a record (Lead, Account, etc.) and somebody makes changes to that record, the update activity feed will show up on your home tab because you are following that record.
• If you are following a user and that user makes some changes to a record, you will have to go to that user's profile on Chatter to see the activity feed unless you are following that record in which case the activity feed is going to show up on your home tab.
• If you are on What I Follow feed on the Chatter home page, it is set by default to Fewer Updates filter for omitting system-generated posts from your feed view. You can update the filter by selecting All Updates to show all updates made by other Users.