A lot of people play bots until they are 30, because they feel hitting 30 means 'graduating' to normals, or in same poor poor judgement immediately into ranked. The transition is jarring and it can take awhile if you fall into this trap to acclimate. You have to first pick yourself up (address your mistakes) before you can improve and that can be very difficult for some people.
There is also the fact that no one plays at a stellar level all the time. Sure, someone's 'bad day' can still be good if they're skilled enough, but no one's immune from having a string of bad luck and de-moralizing flaming making them play worse. I think we can all agree flaming someone doing badly just amkes them play worse, but it happens all the time anyway.
Normals have the assumption of being more 'casual' than anything, where having fun>trying hard. And some people take that a bit too much to heart than others. Ranked has this happen much much less, as well as people's expectations for their teammates and themselves being higher. Ranked imho is a much better community sportsmanship and skill wise. I have had many more instances where constructive criticism and learning happens mid-game in Ranked than normals. So in a sense, yes, ranked is a light at the end of the tunnel =) at least in my experience.
Divisioning normals would result in a nice little target area for smurfs and 'bronze stomping' runs with the added benefit of much less repercussions. So no, I don't thing separating them out works. Maybe making the rank of ho you're playing gainst more apparant after the game, maybe, but not constricting people in an obvious way.
