In fiction, one of the most necessary aspects to a good story is making your main character suffer as much as possible. Make em go through hell and back so that in the end, when they ultimately triumph, the catharsis we as readers feel is so much stronger. Though, for this aspect to work well, the main character needs friends to help her/him along the way.
Think of the best stories (not the best written ones, but the best narratives) and you will see that no matter how down the protagonist gets, their friends are there to provide an assist however they can.
This, though, is a bit of a difficult thing for me. I hav a lot of trouble writing believable friendships because, sadly, I haven’t had many real friends in my life. Many associations, but that’s it. I never knew why; these days I chalk it up to my untrustworthiness and my ability to see past and through peoples’ fronts. Who knows.
Luckily, I have a best buddy, more of a brother, who is worth 1000 friends. And his ability to be a chameleon in any friend-like-situation has helped my writing IMMENSLY. Whenever I am assigning friends to my protagonists, I always fashion them into iterations of my best friend. Its a technique that has proven fruitful time and time again.