Well, perhaps that's because MNF involves no actual effort, given that it's pretty much ripping off other hentai works, tracing them and putting in the exact same moan sound effects over and over again and then adding cheap gameplay gimmicks. Oh, and then there's the numerous occasions where I've seen them outright steal actual 3D hentai work, and just shoehorn in bad English text to make up their own nonsense plot, whilst wedging in those same crummy 'gameplay' features.
Zone's work may be short, but that's because Zone prioritizes actually drawing this shit from the ground up, editing unique sound files, and the overall quality of the end product, as opposed to just shitting out copy-pasta.