The short answer is politics.
You have local producers and you have governments wanting to keep local producers happy and wanting to see those local producers prosper. I think part of it comes from a limited understanding of how the business works. In their desire to help their local people, which in some respects is a positive desire, they are failing to understand that we live in a global marketplace and that we succeed by being able to compete effectively with products from everywhere. When we shelter our own industries, we are actually harming them because we're shielding them from competition, which at some point is going to come along and harm you if you can't compete.
I wouldn't blame the bureaucracies, although definitely they have a hand in it. I wouldn't necessarily blame the liquor boards. The liquor boards are tools of the provincial governments. I think politics is the short answer, combined with not a broad enough understanding of the opportunities that really exist if Canada could open up its internal borders and improve all of its producers by making sure they are world class and making sure they are truly competitive.