All the other Facebook-owned apps like Messenger and WhatsApp already had this feature. The chat page shows the last seen of the user on the top with its name and profile picture. The user can hide the Last Seen from other users from the Privacy menu in the app’s settings.
In Messenger also, you can disable this feature if you want to hide your Last Seen on the chat page. However, disabling the last seen will disable you from seeing the last seen of your friends too. On Instagram, your followers cannot see your last seen activity, but the users you follow or send a direct message will be able to see your last seen. We can also see a “Show Activity Status” toggle in the Settings menu which will disable this feature and hide the last seen from the followers. This feature will also show the “active now” status if you are using the app at the time. Since Instagram is known for its privacy features, this “Show Activity Status” feature can be seen in multiple perspectives. This feature is still in closed testing mode and might be available to all the users in coming months.