When Google introduced the Pixel 4 series last year, it showed off a new astrophotography feature. It's like Night Sight on steroids, taking pictures for minutes instead of seconds. When the Pixel 4a 5G and Pixel 5 came along with a main camera sensor and an ultra-wide lens, astrophotography worked on both sensors, but not anymore.
Starting with Google Camera 8.1 (as spotted by Android Police), you can't shoot astrophotography with the ultra-wide sensor anymore. The reason that it's being shut off is because, you guessed it, the pictures that come out of it are just bad. These pictures also take a fair bit of time to take, so it can get a bit frustrating to waste a few minutes by using the wrong lens. If you try to use it, you'll now get a notification to switch to 1x zoom.
Ultra-wide camera sensors in smartphones are notoriously bad when it comes to low-light performance, just like telephoto zoom lenses. That's just the way it is. Unsurprisingly, companies invest the most in the main sensor, and ultra-wide sensors tend to be smaller with smaller apertures, to a point where night mode doesn't even save them.
It's also worth noting that back in May, the mastermind behind Google's computational photography efforts, Marc Levoy, left the company. He was the one that famously defended the Pixel 4's use of a telephoto lens instead of an ultra-wide sensor, and having left the company halfway between the Pixel 4 and the Pixel 5, Google reversed course at some point.