This exists because there is no formal qualification required for becoming a consultant in general (i am not knowledgeable about Canada) but in my home country (with due apologies to true professionals), some body sharp at ditching others and not able to do any thing decent in life becomes a consultant.
Where most of their knowledge (if any) is from submitting past cases, which often educated people who have been through the process, READ most / all public material posted by CIC know better of.
Technically, No Immigration authority encourages any consultants and gives no special treatments to them.
However, immigration lawyers are a separate story and they usually are far more expensive, but worth their value in knowledge of law.
Update:
+1 to Zardoz yet again, for doing the right thing in appropriate manner