Mostly it's the same reason there hasn't been much interest in XBOX emulation: their backwards compatibility program. You can take almost any physical XBOX game from a previous generation, pop it into a current-gen XBOX, download an emulator-compatible rom, and play the game on the current-gen XBOX. The games don't require an internet connection after the initial download, either. Yeah it's basically a game key card service, but it's a heck of a lot more convenient for most people than hooking up and maintaining four consoles. I have 3 generations of XBOX games, but I use my XBOX One X to play them all because I don't have space on my entertainment unit for the two older consoles. This feature makes original hardware all but worthless except to the most hardcore collectors. I'm not hating on the older consoles, the XBOX and XBOX 360S are two of my favorite consoles in terms of aesthetics, but unless you insist on being able to play obscure titles like Dead or Alive Xtreme Beach Volleyball and its sequel DOAX2 (still the best game in the spinoff series, by the way), they're just not worth the shelf space if you have a newer model. And because this program has been around since the 360, fewer people got rid of their old games when buying a new XBOX, so there are fewer people buying up the stuff that's left. Most of the FOMO that drives the retro market is tied to not being able to play old games on current-gen hardware, so by having backwards compatibility with the vast majority of their legacy library, XBOX eliminates most of that FOMO.
I have heard the rumors about the XBOX Helix possibly getting a disc drive, but I really don't see it getting new physical games. Two reasons: Install size, and recent beta tests. Average install size for next-gen games is certain to exceed 100GB, meaning they won't fit on 4K Blu-rays, which means each game would need to be released on 2 or more discs. If 9th gen taught us anything, it's that today's publishers are highly allergic to doing multi-disc releases, and I don't see that changing. If it exists, the disc drive is most likely for the new disc-to-digital program, which is the next evolution of the backwards compatibility program and recently underwent a closed beta test. While I would love a console that could play 4 generations of XBOX discs, access GOG and Steam, and emulate almost everything, I've had to change my priorities recently. The US (and the first world in general) is undergoing massive shifts. Nobody is going to fix it. Every person we elect, regardless of party, just takes things from bad to worse. Now is not the time for reckless spending like buying a $1500-$2000 console that I don't really need. Realistically, my XBOX One X already plays the three generations of XBOX games that actually matter. I likely won't need to emulate PS4 or PS5 for another 7-10 years, by which time it will be cheaper to do so. And as far as next-gen games go, I really don't want them. I'd have opted out of next gen even if the industry hadn't ditched physical, because the new games are almost always worse than what I already own. Instead of getting a Helix, I'll just see what kind of mini pc I can pick up for around $500-$800. Right now, I need to make sure I've got enough money saved up to leave the country when the time comes.