You just gotta know the difference between friend and acquaintance.
An acquaintance is someone who you occasionally hang around, you can usually get something out of time invested with them, and they can be helpful sometimes. Not being around them is inconsequential.
A friend is someone who's got your back no matter what, regardless of how it profits them. I've bailed my real friends out of **** a ton of times, and they have done the same for me. Not being around them sucks ass, cause you are both stronger when working together.
I have really only a handful of real friends, the rest are essentially disposable acquaintances that I wouldn't think twice if they dropped out of my life.