I really don't get why they went the VM route with WSL2. It seems to totally wipe out any advantage that WSL had over the other VM products.
They're not deprecating WSL1 yet. You can still use it. https://docs.microsoft.com/en-us/windows/wsl/wsl2-faq#what-w...
But if you're looking for reasons, here are some officially stated ones. https://docs.microsoft.com/en-us/windows/wsl/wsl2-about
I/O performance and support for using Docker inside WSL seem like big ticket items. I'd agree with them that the trade-off of convenience sharing files between the two OSes for better support running Linux things in WSL is worth it.