Upvote:5
Unfortunately for you visiting foriegn countries is considered a privilage not a right and also unfortunately for you it is a privilage that people from poorer countries often abuse. That is the main reason western countries require people to get visitor Visas in the first place.
When a visa officer looks at your application they have to make a judgement over whether they can trust you to behave yourself and return home, both now and in the future. Depending on the results of that judgement call they may refuse you a visa, they may grant you a visa but only for a short period and/or a single entry, or they may grant you a longer term visa.
The Canadian government specifies the maximum they will issue a visitor visa for, they do not specify a minimum. Don't think this is an accident.