Why incubate eggs standing up?

[Hoosierchickens]

I've searched for the answer to this and have come up empty. I'm curious why eggs are stood on end in the incubator instead of on their side with the large end slightly higher than the little end? It seems that is a more natural position. Does anyone know the rationale? Has anyone tried incubating with the eggs more on their side? The foam dividers in my incubator would allow the eggs to sit more on their side and still be held in place as they turned.

 

[familypendragon]

I can guess that especially with shipped eggs you could face a real problem with air cells being messed up and the chick being in the wrong position.