I wonder why all these new bundlers don't provide a webpack-compatible API to entice new users. I can't take the risk of investing in a new tool only to find that I can't migrate the last 20% key features that I need. I also don't have the bandwidth to constantly switch between vite, webpack, parcel, etc. every time I switch to a different project.
FWIW that plugin does not make your existing webpack-based code magically work in snowpack. It's just using webpack to bundle your snowpack-based code.
I can only imagine it's because the authors don't care, right? If they cared, they'd build it. But I think most of these bundlers are out to show you how great they are, and how you should drop everything to do things their way.
So, ultimately I think the answer is to say, "No, solve my problem, not yours."