It can, but Linux does not have a stable driver ABI. Whoever wrote the out-of-tree drivers would have to constantly update them whenever there was a breaking change to the kernel, which I understand is relatively common.
nvidia uses "DKMS" to rebuild itself for each running kernel.
Closed source modules like nvidia frequently have a kernel-independent proprietary piece and a kernel-specific (open source) ABI piece. Whenever you upgrade your kernel, DKMS will re-build the kernel-specific shim and re-link the proprietary blob. The result is a .ko tailor made for your running kernel, even though most of the code is in a kernel-independent blob.
It looks like nVidia is open to moving their open driver (which requires a card that as a GSP) upstream [1] but with Rust being killed from the Linux kernel that's probably dead.
