Why do people get upset, when you don't contact them and it's clear that they have moved on?

I’ve noticed allot of people that I used to hang out with clearly move on with their life and they don’t make an effort to contact me, but when I contact them, they complain that I don’t make an effort. I swear communication is a two way street, I feel it’s up to me to make first contact.

Express? Opinions?