It says a lot about a company when you can buy their products at walmart. The point is that Weider catters to the mainstream. When some wannabe wrestler sees Weider Muscle Builder ads on Raw, he will go out and buy it.
Supplement companies can put pretty much what they want in their products. Why would Weider put in good quality ingredients when they can make more money selling to people who wouldn't know the difference anyway?
The supplement store ownners I know do not carry any Weider products on their shelves, FYI.