Is there a reason why the ''recently played'' tab was removed?

Good question. I wonder why they did that.

Last time I checked it's still on PBE too. Either way it's a sign of incompetence: either incompetence to fix a bug or incompetence to communicate with the playerbase.

If you mean the thing that lets you see and friend people you've recently played with, it's in the "Add Friend" button.

You can right-click them to view their profiles as well.