I don't see any issues with why we can't have as many friends as we want, and what's the reason for automating the removal of friends after some time?

This "limit" would arise more problems. In the event of reaching the limit, it'll be ridiculous that we would have to delete our "least favorite" friends to make room, everyone would just have a dilemma, not to mention the dramas that would unfold if certain friends talk about why aren't they part of someone's friendslist anymore.