I'm not sure if that's the case.
I know at least a few people who just learned that Bing exists and switched to it in the last few weeks. This, of course, is just a random observation.
Anyway, Microsoft claimed in this March that they have now 100 million active Bing users [1]. It's a little compared to Google, but it's probably a huge success for them.
Actually, I think it's a good thing they've built a separate app for that. We used to think that one app that rules all of them is a good idea. Not always.
Classical music has a lot of nuances (some of which are listed on the announcement page) and from UI/UX perspective it would be quite difficult to mixed all these details in the standard Apple Music app.
I'm now wondering what Spotify thinks about this matter. Do they plan to highlight classical music like Apple did. I don't know.
Apple and Google want to show off the latest features in iOS and Android, so incorporating these into your app will make sure you have the best chance of getting featured.
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I think it's not fair not included Windows here. Windows 10 also have excellent features.