How about some examples of what you are talking about. Some people use the wrong chemical for a certain weed. Many people try to kill clover or chickweed with Weed B Gone, when in fact there is another product specifically designed for those weeds. Nutsedge is untouched by most chemicals as well, unless you use the appropriate one.

not a gimmick, you probably are using it on wrong types of weeds or not applying correctly. weed b gone takes about 7-10 days to see results.

When used correctly, weed b gon is highly effective for its purpose.