As much as I get frustrated with the way certain manufacturers determine sizes and cuts (I'm looking at you CM with those tiny, skinny trousers in a size 12 that couldn't accommodate my size 10 foot, despite the fact I have other CM trousers in a size 10 that fit perfectly), I also think that, logically, we come in so many shapes and sizes that it's actually quite amazing that so many of us can fit into much of what is out there, without major alterations, given that many items only come in 4 or 5 sizes. I need something that fits comfortably over my broad shoulders, while your dainty shoulders get lost in too much fabric, but we both ought to "fit" a size M according to our bust measurement. Same goes for my non-existent butt and straightish skinny hips which could have the same width measurement on the sizing chart as a much smaller woman's very curvy bottom half.
For what it's worth, though, I do support Sveta's frustration with companies like Zara who, for some strange reason, offer some designs in an XL, but not others. If the garment is too large, alterations are an option, but, if it is too small, I'm automatically sized out because of my shoulders.