Presumably there are all sorts of kulahs used by various agencies on many products. Does that mean one needs to research every product? What about Bishul akum questions that come up on nearly every product? Wouldn't it make more sense to just exclusively use hechshers that conform to one's standards?
bishul alum doesn't come on nearly every product. Probably not even on 1/4 of certified products.
Also, many people on this board have asked specific questions regarding bishul akum. Grape juice is a known red flag ingredient with many known kulos (many of which I suspect would shock quite a few members on this board). Therefore it make sense for someone to ask questions regarding grape juice.