Aside from them being the most entertaining companion(s) one could ever have, friends are people who will listen to your problems and raise your self-esteem when ever you're despondent. While it remains true that friends could serve as your counselor, abusing that expectation could result to isolation from them.
True friends are indeed supportive, however if one is morbidly consumed with negativity, blind to possibilities and denies any real solution to their current problems or take any significant actions, these friends will leave him/her. It is unfair to see your own life falling apart and lament in front of them and not consider the problems your own friends may have. If they never mention a word of it, perhaps it is too painful for them to even discuss it and that brings to question how serious your problems are in comparison. Perhaps it's not half as bad as their problems and you making a scene of it whenever you meet them or hang out, could annoy them.
You hang out to have fun. You want confessions? Go the Church or a temple, mosques -- whatever your religion is. At Christians and Catholic Churches, they have confession boxes there where you can talk to the priest on how you have sinned by hating your boyfriend/boss/sibling/parents/grandparents/jobs for whatever reasons you may have. Don't expect your friends to listen to your rants about your miserable life, how nothing is going your way, etc., for hours on end. It's just too much responsibility. Your problem has nothing to do with them and they're not responsible for your own happiness. YOU are. If you want to rant, talk to your God. If you're an atheist, talk to a hole on a ground and hope it'll reach the other side of the world where your bad vibes are vanquished like vapor.
So what are friends? Friends are your companions and sometimes they can prove be your life-support when you need it most. Yes. True friends could lend you money, material goods, a roof to sleep in and more with a condition that you can bring your life back on your own two feet. In short, friends are temporary supporters when you're facing a crisis. One must never, ever depend on them for too long. They're not your parents.