Pen everything down, remember withholding anything knowingly amounts to misrepresentation and that is grounds for disqualification. They require your job history etc. as it is one of the factors to establish your residency requirement, and to make sure your were here. If you don't have a job they'll use other factors, kids schooling, number of travels or lack of it etc. etc. Offcourse no one really knows for sure except the officers dealing with the applications.
Filling taxes and having access to the CRA records is an another tool to establish that you were here. Also as per cic website, it shows that you are fulfilling your duties as a resident etc etc.