Context is everything, in context PBR is decent beer. I say this as someone who knows PBR as "the beer brewed downstream from Chicago". [Re-read that and make sure you have the advertising slogan "it's the water" firmly in mind.]
First, it is a mass market American beer. It is brewed to be served slightly warmer than frozen, to accompany pork rinds, Cheetos, nachos, hot dogs, hamburgers and BBQ ribs. Chilled to a point that would render even better beers just a bit more flavorful than bottled water, it is a good match for such fare.
Second, it is up against the likes of Olde English 800, Schlitz Malt Liquor and other fine brew in the 40 oz. format (or others sold mainly on the point of being cheaper by the case than beer like PBR). Indeed, after buying that 12 pack of PBR, you can hold your head up proudly among peers who drink effete things like Champale, Thunderbird, Boone's Farm and Night Train because at least you aren't a cheap drunk, nor have you succumbed to drinking light beer.
Last, but not least among horrors, it survives in the American distribution system. The same folk who have managed to keep Chock Full O'Nuts and Safari (colored sawdust sold in large cans mislabeled as coffee) on the shelves in supermarkets are also stocking the beer.
Context is everything, I'm going to go out and drink Yanjing at something like thirty cents per 600 ml bottle. It goes well enough with skewers of grilled lamb and the somewhat Turkish style dishes of Western China.