Separation of Screen and State

Ok so there is fragmentation due (in part) to companies "Skin" i.e. Motoblur, touch wiz, or HTC's. These "skins" can hinder the update value of the phone (understanding that carriers get in the way as well). If Google knows this, which they do, why can't it be addressed in a different way? Can't there be some sort of "re-coding" to allow the skins to be more them like instead of it being so tied to the core? Much like CSS to HTML? I am no programmer so this may sound stupid so I apologize. But if the skin can change by creating a separate style sheet then the phone could update the core while the rest could just be a style sheet update.