People are giving up on stereo because they are lazy and cheap, and it takes a lot of,... you know,... like,... space? "Heck, this other cute one still *Plays* *My* *Music*, right?" Besides, if you are going to buy a tiny speaker and wedge it onto your kitchen counter, in the corner, shoved back echoing between the countertop and the upper cabinets,... well, who the heck *cares*?
Seriously though, it's pretty basic: the difference between no-music vs. having-music, is much much greater than the difference between mono music vs. point-source stereo music vs. separated channels. And in some places, like the kitchen in my example, arranging stereo for multiple areas is tricky. People just don't get that they could buy 6 speakers and play them all less loudly, then arrange them for sink, stove, and table stereo images, plus a decent L/R vs. R/L "traveling" image. Even understanding, they still don't want to bother or don't want to spend the money. It's just too much trouble, if all you really want, is to whistle while you work. Apply the same only-slightly-exaggerated scenario to other rooms of the house. Just grab a speaker, toss it wherever you are. Lather, rinse, repeat.
The same question gets asked of Sonos, where the Play:1 is cute and compact, vs. the Play:3 and the Play:5 try to do stereo from a single box. At least with Sonos, the answer seems to be "so just buy one Play:1, and if you don't like mono, buy a second one and pair 'em to stereo." (That's even true of their Play:5; if you turn it vertical it goes mono, then you add a second unit.) The Bose Wave Radio is another example of point-source stereo. B&W Zeppelin, Naim MuSo, same idea. At least the A6 aimed the speakers slightly outward so it would sound 2-channel at a medium distance. I have heard all four; all are "just fine." I happened to like the A6 best. Does stereo matter? I dunno... To me, it only sounds "right", i.e. stereo image w/non-exaggerated bass, if you place them away from the wall, and sit 4 feet away. But that's just me. I put 6 ceiling speakers in a kitchen once... They liked it. But they also added a Play:3 in the corner of their dining room.