The big brewers want people to get all caught up in the semantics. The situation is best explained by the movie, Beer Wars.
Here is a short explanation -
http://www.pajiba.com/film_reviews/beer-wars-review-why-we-drink-piss.php
It's not just about advertising and marketing.
Beer Wars also takes us through the myriad of obstacles that stand in the way of smaller breweries and craft beers trying to enter the market. The 40,000 state and federal laws that regulate the beer industry, for instance. Or the fact that Bud/Miller/Coors owns a monopoly on grocery store shelves. Whenever they feel that their space is being encroached upon by a smaller brewery, they just create another beer or another size to take up more space. That's the reason, for instance, that Budweiser Selects exists -- it's not because it taste different than Bud (in fact, there's very little discernible taste between Bud, Miller, and Coors) -- it's because it allowed Budweiser to take up another six feet of shelf space. That's also why you can get Bud products in cases, 12 packs, six packs, cans, bottles, and even mini-cans: because it takes up more space. That's why you have to spend 10 minutes searching your grocery store shelves to find the better beers, if they exist at all. There's also the massive beer lobby, which is bigger than the gun and tobacco lobbies combined, which works diligently to assure that the status quo remains.
