Ive "cleared" out so many people over last few years.
Notable reasons:
A friend that would text to "check in".. this meant 3 or 4 texts digging for how my life was going, so I would open up, then ask her how she was and her family and I would get "ok"
Suggest to meet up, I would get a none committal response. I got the feeling I was nothing but gossip. So I cut it off.
She tried for ages to get back in touch, going through mutual friends to ask me 'why'
She gave up in the end, I think.
Another friend, which hurt, been close for years, but steadily our friendship unravelled, I think I tried to hold on for far too long, he was quite lazy with it, and I found less and less in common with him.
What broke it is me telling him something in confidence and him going straight to the person in question and telling them, which caused some problems when I was already going through a tough time.
We talked, he apologised, and we saw each other a handful of times after that, but I found that I just felt like I couldn't trust him, and that I felt resentful towards things going well in his life, in the end I changed my number and cut it dead.
He has since tried to initiate contact and ive been encouraged to contact him, as "he has no friends and feels lonely" (this is untrue. The circle with his partner is huge and consists of my old friends)
I resented the loneliness line as I have felt very lonely at times, where as he and his partner have active social lives and friends/family... but I am now also suspicious of people and aware of my own feelings when I compare myself to others, I think ive generally been happier with less people around me and im making better lifestyle choices.
Its a mix of my disappointment in people, and my own personal issues that have made me go AWOL, and understand why others have, historically done the same in the past.