security check is not as easy as you think, it is not matter of 2 min to look at a black list on their system and then decision made!
i want to share this article with you, i found it somewhere on this website, and it sounds so logic:
Security & Criminality Checks:
A part of the b/ground checks is the 'Security Check'. It commences after our med results are submitted to the CHC. This is a major activity -mainly concerning our 'safe inclusion' into the Canadian Soil; vis-a-vis, Political, Socio-Econmical, Anti-Social disposition, perceived Threat to Canada's integrity etc. This gets us the SDEC, CDEC & SECCRIM.
This is a serious & time-consuming stage, involving many agencies, including CSIS, Interpol, NASC, Database Checking & touch-base with Local Police. Many things are considered here... the No. of countries visited, Applicant coming from 'certain' countries, ex-Servicemen [including Law Enforcement services], Prolonged stay in a country w/out sufficient docs to prove cause, frequent traveling to certain nations, your *Name (?), Inter-Religion/Nationality Marriages etc.
after reading that you can now imagine how long it takes to get done with each of those agencies who i am sure they all have backlogs regarding the too much applicants around the world to many countries not only to canada..