DOS version already use it. Just the work to do the same with the Windows version...
It's not that simple (it should be more simplified on how the coding is done for it, but that's not within the scope of my arguement).
In DOS, you had to select between non-standard resolutions and VESA available/compliant modes...
In Windows, you have options between non-standard resolutions and mostly Windows friendly resolutions (and somehow we now have one laptop res available)
Since ZSNES Windows automatically uses 16-bit modes by default and there is NO benefit to allow 32-bit or 8-bit modes (8-bit modes will cause people to moan about "bugs" that don't exist because transparancy is not applied).
Then again, I don't think you get it.