Some people never reply back. WHY?!

Hi guys,

Today I wanted to ask you a question. There are some people on my friends list which never EVER message me back unless they want to play with ME, which is almost rarely. Also, some are even my Skype friends which used to know about two years ago. However, two years ago they always wanted to play. The most recent incident was when I asked my best (online) friend if he wanted to play a game together, but he never replied. A few minutes ago, he started going in a 5V5 ranked queue with someone he told me he hates. I know you guys don't want to be involved in social life, but please, why do these people do this? Even people who are not my Skype friends do this. Do they just hate me, and if they do, why haven't they defriended me yet? Please don't be negative when replying to me.

Thanks, bye.

UPDATE: All of them are playing ranked 5v5 and they made some shitty bronze team which consists of little shits worse than me (other than the good people they recruited from online which are their coaches). I feel left out :(