Per capita income doesn't mean the population will buy your product. From the data points it seems that portable Hi-fi is mainly an East Asian thing, so targeting Europe/NA even when they have money doesn't make much business sense, that's like trying to sell eco electric 2 seater city dwellers to the SUV crazed NA market - you've got to pick your market wisely - no product can be completely global with universal appeal.
Streaming may not be the future - because companies that do streaming are actually really struggling to make profits, they have users but aren't making money, that's not a good sign for the future of the market. Just like everyone was betting on free ad supported video streaming is going to be the future income revenue about 10 years ago but that actually didn't happen. Sony had specifically said that the feedback of ZX1/2 users is that they don't like Android on it. So while in the West the ZX2 may have gotten some sales due to Android, Sony's own data says otherwise and that was their choice. Again since the East Asian market is where DAPs sells the most and Sony's gotten feedback in that way, just maybe consider that streaming may not be as big as you think it is.
FWIW Sony's business is in BOTH streaming and downloads - they run their own music DL site in Japan, and they supply their music to streamers as well. Sony actually has a stake in Spotify of Japan - they "win" either way no matter how the customer chooses yet they still decided not to put in streaming. I think they actually have more than enough numbers and data points to support their choice here.