Empty Promises

So after the past year or so I've learned who my real friends are. I've had so-called friends talk about how they'll be there for me and act supporting and yet it's all empty promises. If they do check-in with me it's for their personal benefit. However, when they're going through hell they expect me to be there. I just don't understand how people can act this way and live with themselves. It's hard not to think that everyone is out for themselves when even your "friends" treat you this way.