A phone lens turret is possible in principle, but it conflicts with how smartphones are designed.

Main reasons:

• Mechanical complexity: A rotating assembly must stay precisely aligned so the lens remains parallel to the sensor. Doing that in a very thin phone takes space and adds failure points.
• Sealing and durability: Moving external parts are harder to dust- and water-seal, which phone makers try to avoid.
• Space limits: Bearings, supports, and the rotation mechanism all consume space. Some phone telephoto cameras also use periscope layouts, which don’t fit naturally into a simple turret.
• Computational photography: Modern phones often use data from multiple cameras at once for scene analysis, depth mapping, and image processing. A turret would allow only one lens to see the scene at a time, reducing those advantages.
• Product design and user expectations: Buyers generally prefer simple, sealed devices with no moving parts. Manufacturers also prefer software/electronic solutions over added mechanics.

So the issue is not that companies couldn’t build one, but that today it is usually less practical, less robust, and less useful than multiple fixed camera modules.