It's probably a project that is helping at least hundreds of thousands of people (maybe even millions), and it is getting quite mature, so I don't see any reason not to do it.
"cheaper"? Wine is free software, whereas to run Windows you need a Windows license.
At this stage working on something like wine seems like a misguided effort. I use windows as my primary desktop OS and it works well. For non-windows users, a vm solution would be way better than a kluge like wine.
If I still used Windows as my primary desktop OS, I wouldn't care about wine either, but then again I wouldn't be the target market, now would I?
I used Ubuntu as my primary Desktop during the stone age of Vista and even then, using Wine was a painful experience compared to just switching to Windows.
I agree on the effort part though : it's a lot of time loss on something less and less useful nowadays.