In particular, Wayland requires KMS support from drivers, which NVidia can't implement due to it requiring GPL-only symbols in the kernel.
It also assumes the use of DRI2 and GEM, meaning a major redesign of NVidia's driver would be needed and they wouldn't be share nearly as much code with the Windows driver as they currently do.
KMS, DRI2, GEM, etc. are open-source technologies which pretty much do the same thing that the binary blob does internally. Nvidia just can't be bothered at this time.