And they all suck.
I won't argue with that, at least today. All the old regional beers faced huge competition from Millweiser. They got squeezed out of the "regular" beer market, and had the choice of either going up market, like Anchor, or going down market into the "popular" (cheap) beer market. Once you have taken the "popular" beer approach your selling point, except for a bit of residual brand loyalty, is price.
Again, Millweiser has you at a disadvantage, because of the efficiency of their huge, automated, breweries and distribution systems. They can make, and distribute, cheap beer cheaper than you can. It makes economic sense then to close your brewery and just have Millweiser slap your label on bottles of the cheapest corn and rice based swill they can turn out, uhhhh, I mean of course, just have Millweiser custom brew your beer, according to the ancient family recipe ; )
Of course that leads us to the sad state of mass produced domestic beer. Go into your average gas station, look at the various brands of beer. Then look closely at the labels, or better yet check on the internet, and see just who actually makes all those beers. Apart from Coors, and a few surviving regionals, Anchor, Shiner, 95% of the domestic beer there is Millweiser.