I don’t like this limitation. Using an inbox (people you follow) and requests (people you don’t follow) is a much more open approach.
Discussion
Agree. While I understand there are people who get overwhelmed inboxes as it is, there are those of us who have stayed away from public presence on social media who have something positive and constructive to offer and are here with that intention. If you only are open to your own existing circles there's a lot of value you'll probably miss.