you would have to ask those that are interested or perhaps email some off ebay and ask them why they bought them over a full a cab.
me I can't tell ya what others were thinking but perhaps maybe they dont have the room for a full size cab or cabs but it dont seem like a bad optional piece to those that do want them as it was mentioned prior already.
asking that is kinda like the bartop itself and the same silly question would apply.. why that over a full cab then?
but now onto me personally I already have a full 26" nanao cab and a 39" showcase and I now want a bartop becuase either of them will fit in my pc/lab/mancave.
but I would think if it were me and they were available instead of the bartop hoggin a shelf or pc desk it is now in the corner inside the base with a monitor or shelf on top of it so no space is lost now becuase I can put something on it if it were me though.
a slide out keyboard drawer would not hurt the looks for it all either and give it more of a desk look.
sure the showcase would fit but is also would be like parking the truck in the living room.
another good example is if you only own a car it's a ---smurfette--- driving down the road with it on the roof
another example have you ever tackled and tugged a full size cab up your 2 flights of apartment stairs at 56 years old all by yourself without a scratch to either?
just a couple reasons why some may want one off the top of my head for ya.
in the end it comes down to prefference of the end user friend and there is already a market for them apperently.