I'm currently playing in a sci-fi campaign, in which I provided the DM with not just a backstory, but also a list of contacts and business partners of my character, and descriptions of all of them. In a way, these side-characters say more about my character than the backstory, which I thought was an interesting way to write a character for a change.
I've noticed that quite often when players write a backstory for their characters, these characters don't seem to have any life, friends or family. And as such, they don't feel like real characters to me. Why are all PC's orphans with no friends and no family? Why don't they have a job, and other people that have a role in their lives?