Why do so many size guides only give incomplete measurements? Bust measurement is given, but forget about shoulder width, and you're fairly lucky if you get the length of the garment. Do they think women are stick figures with breasts?
I'm a slim woman with a somewhat longer torso and somewhat broader shoulders. I do actually need to know if your top will cover all my top and will not be too tight on my shoulders and cause discomfort.
Similarly, the randomness of fit! Not even between shops where you're X in one and Y in another, but from the same shop, for the same type of item, from the same collection. Satisfied with the fit of one t-shirt, I got another, this time online, for the same size and the same collection: completely different fit, but too late to return (and of course no size guide there at all). Trying on jeans in a shop: there were some that were far too long, some I couldn't even zip up, etc. But all the same labelled size (by width and length measurements!) What's the point of it then?