A reasonable number of thin coats of wax polish (~10-15) will still allow water vapor to pass, and therefore allow the shoes to breath. As you start to build up a thicker and thicker barrier you begin to suffocate the shoe leather.
Also, keep in mind that the majority of the moisture evaporating through the shoe leather as you wear them is going through the quarters and vamp, where your feet have the most contact with the shoe upper. This is just one reason you should not have a lot of paste/wax polish on the vamp or quarters of your shoes.
The toe puff (on the style of shoe you would spit shine) is also going to impede evaporation through the toe (even more so if it's a plastic toe puff).
Another thing to note is that a fair amount of perspiration remains in the shoe liner and insole and is absorbed into the more porous shoe tree wood, and/or evaporates into open air, when the shoes are taken off and stored.