I'm curious why you think it reduces design costs to put less information on the screen? My experience has been the reverse -- the companies that chase trends (including but not limited to low-information-density screens and using mobile-first designs for desktop applications) also tend to spend more money on UI design compared to other companies.
The question is for whom it saves costs? For the developers of UI framework it certainly saves cost to treat the desktop as a second rate platform and to focus just on mobile.
Developers of desktop applications have to pay the price, by working around libraries and frameworks that do not consider them as a first tier clients.
things on screen take effort. less things, less effort
(At least in enterprise software the data density typically depends on who makes the purchasing decisions. If novices and/or business folks are the ones making the pick then the software will look sparse. If technical and/or experts pick their own tools then it'll be dense and efficient.)
> Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away.
That is the right reaction to over-complicated baroque creations.
Important to note, that oversimplification is possible. (There is point at which removal is no longer benefitial)
though, excessive white-space does not really scratch the "efficient interface" itch