Loses hurt, and as individuals, we handle situations very differently.
For the fact that we do not know how to handle situations of loss correctly sometimes, we prefer to hold on to unhealthy relationships instead.
Life happens and for the sake of our sanity and progress, there are certain people we need to stay away from and wish them well from a distance.
Well, a relationship might not be unhealthy, sometimes it just doesn't work and people have to go their separate ways. In this type of loss I think it teaches the appropriate lessons that at the end of the day, we're all we have and that's how it'll remain.
I agree, it doesn't need to be an unhealthy one before people finds their separate ways. It indeed teaches the concept and importance of value.