Some reasons you might want to file are if you had taxes withheld and want them refunded; if you're eligible for the Earned Income Credit (you might get a refund even if you didn't pay taxes), if somebody else is claiming you as a dependent; or in some cases you'd need to file if you're getting health care from some version of Obamacare or if you owe social security taxes on income you got a 1099 for. There might be other reasons, IRS Publication 501 lays them out. You can read it online here.
