Two common situations:
1) people want to take bundled distribution (of mono, monodevelop) and build from it, instead of building from source code repositories.
2) people want to get binary packages (from https://www.nuget.org/)
and run them as is.
My wish is different. I want to have one .ebuild file per source code repository. This should allow development under gentoo, not only running applications, which are developed under windows.