Explain the success of beer stores,coffee shops or restaurants... Why buy it when you can brew it? Cannabis will be no different. People are lazy.
Itsme.
'People are lazy' is a lazy way to try and justify the prediction that very few will grow their own. 'People are lazy', and yet more and more are growing their own food in the interests of knowing what's in what they're consuming (sound familiar?).
The fact of the matter is that thus far, private industry hasn't been able to innovate at scale. The 'free market' is nothing more than a state-sponsored market with ridiculous regulations that stifle innovation. After legalization, and hopefully sensible growing regulations the real 'industry' innovation will start.
Beer stores : Craft breweries are one thing, but it's not feasible for someone at home to product their own vodka, gin, etc. Everyone seems to be falling over themselves to shoehorn cannabis = alcohol, and one of the only reasons why is that it's an easy 'in' for legalization. That's no longer a concern, so this argument is going to start falling away, the sooner the better. In short, to grow cannabis, you put a seed in the ground, no matter what strain. Entirely different for alcohol.
Coffee Shops : This is an even worse comparison, coffee shops are about the social experience, and in that respect vapour lounges have been around for a long time, and have been very successful (until Wynne's anti-vapour lounge legislation). If you were to look at the numbers on total amount of coffee beans consumed at home vs people who buy starbucks, I don't think you'll find a very compelling argument on that front either.
Restaurants : Again, all about the social experience. Probably the worst comparison out of the three. People buy their source material, and create meals at home for the most part. Very few people can afford to eat out all the time.
In short, we've never seen a truly free market when it comes to cannabis, so predictions based on either the niche MMAR model or the restricted market of the MMPR are speculation at best.