Possibly because you've never ridden one?
It took me 4 different adventure bikes to realise that, while I like the concept, they just don't work for me.
The R100GS (early, pre frame mounted fairing version) went after my first long (250 mile-ish) run on it, as I could'nt face taking it on my planned 3 week tour abroad due to chronic discomfort. Replaced with a Moto Guzzi Mille GT.
The XL600V Transalp did get abroad, but went after 18 months as I was not happy with the handling - too easy to have the skinny 21" front wash out when riding enthusiastically - even after fitting road tyres. Replaced with a Deauville.
The ETV1000 Caponord had the comfort & handling, but "the wrong engine, Gromit" - a viby, flywheel-less lump with no bottom end, dismal economy & a godawful "slipper clutch" that tended to slip at inappropriate time. That went when I got back from a Continental tour. Replaced with a Moto Guzzi Breva 750ie.
The NC700X DCT just didn't fit me & was uncomfortable due to slippery, forward sloping seat & the over wide "tank". That went on return from a Continental tour. Replaced with an NC750S DCT.
Similarly took my ownership of 4 different in-line fours to twig that it was the engine layout that didn't work for me, not the individual bikes - seems I am pre-progammmed to prefer twins in various forms !
Adventure bikes are fad, just as SUVs are the current fad in the car world. Hopefully the manufacturers obsession with them (in both 2 and 4 wheel camps) will pass.