The online sign feature. Steemit is from from a platform with users from the same location. Over a million users now means many people from different locations and different time zones. It may be midnight at your location and early morning elsewhere. This is varied timezone.
An online status with a green sign near the profile picture with offline and away sign too will let users know who is online and who is not. This has lot of benefits. Users can use this effectively when making conversation. They know what time the user is online. In the event of making a post too. You can know when the majority of your followers are online.