Who I maintain relations with and who I don't is not other people's business similarly who I follow and who I don't follow should not be visible to anyone except me but that is not the case.
I can go on and on about similar things but the bottom line is everything on Instagram is designed in a way such that it generates more activity on platform and ultimately more revenue. This is true for almost all the social networks though. A social network that respects norms of our society and does not attempt at maximizing revenue at users expense will probably fill the void left by the existing ones.
It's not just about (B). There is a tricky balancing act involved. A company that does too much (B) ends up with an app that users don't like and stop using. A company that does too much (A) produces a beloved app right up until the point that the company runs out of money and folds.