As explained by BuzzFeed News:
"Instagram launched its “Following” tab as an early feature back in 2011, long before its Explore tab debuted. At the time, Following was the best way to discover new content, since it would show you things your friends were liking. But that’s no longer true now that Explore has established itself as the primary means of discovering new stuff on Instagram."
So, in many ways, the 'Following' tab is somewhat obsolete anyway. In addition to this, Instagram says that few people have been using it, and many may not even be aware that the tab exists.
Instagram chief Adam Mosseri says that the change is also related to simplicity, and keeping the app focused on the key functions people use.
And then, of course, there's the additional consideration of the embarrassing Likes it can uncover. Like a picture of an IG model and your friends and family can see it in the list - and that's probably the tamest variation of this type of discovery.
As per Instagram head of product Vishal Shah:
“People didn’t always know that their activity is surfacing. So you have a case where it’s not serving the use case you built it for, but it’s also causing people to be surprised when their activity is showing up."
Given the rise of Explore, it's a minor change, but still, any variation in process will have an impact, and some users who loved the 'Following' tab will no doubt voice their displeasure. From a brand and marketing perspective, it does take away another surface for potential discovery, but the impact, given the usage behaviors noted by Instagram, will likely be minimal.
Instagram will be removing the following tab for all users over the course of this week.