Sony still has ten percent of the Japanese mobile market. Granted they'd be happier to be in the winners circle, but you've seen Sony's product strategy, selling a handful of phones to 10 million people is a business they're comfortable staying in. They'll sell you five different audio recorders, after all.

Edit to add: the most popular vendor, by far, is Apple, with more than 60% of the market. Steve Jobs studied Sony very carefully, back in the day. It shows.