Why do people add me on instagram then unfollow weeks later?

So they request to follow an even like the odd pic. Then they unfollow for no reason. People i've known years from school. Ones who think their hot aswell but aren't. I was nothing but nice to them. Some weird bitches in the world. Or could my pic of white girls with no lips offended them?
Why do people add me on instagram then unfollow weeks later?
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