Probably being a Commonwealth country, Canada preferred IELTS. It could have been better if CIC give an option to choose any of these two by the applicants:
From IELTS and TOEFL websites:
IELTS : Accepted by most Australian, British, Canadian, Irish, New Zealand and South African academic institutions, over 3,000 academic institutions in the United States, and various professional organisations. It is also a requirement for immigration to Australia, New Zealand and Canada.
TOEFL : Most widely respected English-language test in the world, recognized by more than 8,000 colleges, universities and agencies in more than 130 countries.