1. It sets a frontier between your “true” friends and others. What if I don’t like someone anymore but don’t want to offend by removing them from my Millow? What if someone wants to add me but I don’t think of them as close enough to be on mine?
2. I personally do this on Line and WhatsApp. So I really don’t feel like adding yet another social app
3. The reminder part is weird, if they really are close friends, I don’t need a reminder to call them. So this feels more a “remember to call grandma”.