The most common reasons to file tax returns are if you are expecting to get a refund or credits from CRA. If you have taxes due then you should also be filing on time...even if you don't have the money to pay since the penalties and interest can be frightening!
If you are expecting credits from CRA they are usually based on your family income so it is also a good idea to file as a family. This helps to ensure the proper information is sent at one time instead of having CRA pair the accounts up which could delay any money coming back to you or cause confusing between transfers from spouses and/or children.
If you have a student in your family you will want to have that person file with you so that the tuition transfer can be optimized. Make sure that the student downloads the T2202a form to maximize the transfer and credits too.
More information is available in the August SmallBiz Builder.