Xbox hasn't officially revealed console sales figures for years at this point - since early on in the Xbox One generation. During that time, Xbox sales were clearly behind the likes of PlayStation 4 so that surely played a part in Microsoft being sheepish over hardware figures back then, however these days it's not the only reason.
Phil Spencer has been clear that Xbox's success isn't just about console unit sales anymore, and Xbox CFO Tim Stuart talked about this a little more at a recent summit. Stuart says that the focus for a while now has been on "content and services", not just hardware sales (thanks, Gamespot).
"At first it was like, 'What are you doing?' 'You're the Xbox business and you're not giving us console [sales numbers], that makes no sense.' But it was really the first point of us saying, no, no, it's about content and services."
Also speaking at the summit in relation to Microsoft increasing its share in the market, Stuart discussed how the team measures success now. Again, it's all about using content and services to grow Xbox's piece of the gaming pie (thanks, TechRaptor).
"Success for us is we can keep growing that content and services revenue double-digits. [...] If we can grow faster than the market is growing, we are taking share in the gaming market.
And that's where we want to be. It's a 250 billion dollar market. We are not 250 billion dollars."
Regardless of whether Microsoft announces its figures publicly nowadays, we often get various sales updates via other sources. Recent court docs regarding Activision Blizzard revealed lots of facts & figures about the Xbox business, and outlets like GamesIndustry.biz often share numbers surrounding Xbox hardware and software sales on the regular.