Across North America there are mainly two reasons for requiring guides for non-residents. In many instances it is safety related to protect relatively inexperienced hunters hunting truly wild ,remote areas for potentially dangerous game. In some cases severe weather, mountainous terrain, the use of horses for access, etc. are factors.
The second reason, however, is mainly a financial one. It funnels business and revenue from outside the state or province to local outfitters, guides, hunting resorts, etc. In addition to the direct hunting industry, motels, restaurants game processing outfits all share in the bounty. Its kind of a full-employment act for guides and outfitters.
I have had three Alberta hunts. Two in Lac LaBiche for whitetail and one south of Calgary for mule deer. In all cases the guides were absolutely top-notch. They were highly experienced, competent and hard working. I couldn't ask for better. You just have to be very careful and do your homework before booking.