I find that so very saddening. I understand what is said, and yes I guess it is true to an extent. We all have friends for some reason or another and yes, we benefit from it. But surely that's the point? Not in a negative way using the word parasite, but by an even, a mutual benefit of friendship. If there was nothing in it for a friendship then surely we'd not bother? A friend can be fab, someone who helps you, someone who you help back with ease and even pleasure, someone to trust and have a good time with. Benefit yes, and a rather nice one.

People moving on is natural. We are always changing as people as the years go by, so it's totally natural that we can lose touch with some folk, even tho they were once fab friends. It may be as simple as nothing in common anymore, without ill feeling can be enough to drift apart. This isn't a slight on anyone, it's not a crime, its just the nature of friendship sometimes.

I think if you feel so strongly that you think of friendship like being a parasite, then I would say that that perhaps some of your friendships were never equal or healthy in the first place. I could argue that they were not a true friend, but more like a user. But it would be a real shame to label everyone the same.