Because Meta doesn't care about PCVR. There has been no noticeable improvements to Link in a very long time. All updates are targeted towards standalone Quest 2 functionality, which is explained by it being the main focus of the device and standalone VR market being the hot thing right now. Still, it's a shame, they marketed Quest 2 as "all-in-one VR" initially, but now seems to abandon this concept.
Example: current virtual audio driver has compatibility issues with certain hardware they just don't care to try and fix. At least they could've added some debug functionality to change audio buffering settings, that would've most likely allowed people like me to work around the issues. But no. Why bother, right?
For me, Cable Link is how I use Quest 2 99% of the time. I just don't find most standalone apps appealing. I bought Quest 2 for image clarity, and what's the point of this amazing screen when you use mobile GPU to render the image? Desktop GPU will always be way ahead in capabilities to render beautiful virtual worlds, because of physics (approaching physical limit of node size push newer GPU's to be larger and more power hungry) while the main appeal of next-gen VR headsets is the reduction in size. There is a big push for streamed gaming, but it doesn't currently work even for slow TV-gaming for many areas because requires good internet infrastructure, not to mention the low-latency requirements of VR applications. So I just don't see the PC VR being replaced by anything if you want to experience beautiful VR worlds.