Aye Up,
I take your point(s) IC_Rafe - but it is a question of horses for courses.
If you
need low profile - i.e. weather/application, these types of bivvy are ideal.
I've seen people on the point of hang gliding with their tents during a squall in Wales whilst the Carinthia has been stable.
I've been hunkered down in moments whilst others have still been pfaffing with fly-sheets/tarps etc.
I've laid up in close proximity to other 'stealth campers' and looked-on whilst they have shown out.
Let's not forget that this style of shelter
stems from military origins (sniper-bivvy) and not bushcraft/outdoor pursuits-world, a mistake we often see made on the site when people slate a piece of kit t'd up for bushcraft without taking into account its true purpose.
My view is that hooped bivvies and tarps are probably the most versatile kit-set as they provide a number of options even if there is a (relatively minor) weight penalty.
Despite its limitations I wouldn't part with mine.