There's another difference -- uniformed guys (and gals) are usually all about serving their country. As MapleLeaf points out, not getting a seat up front will have little/no influence of their choice of career.

The pols, on the other hand, are all about serving themselves, what's in it for me, will this get me more money/re-elected, etc.

Sudden thought -- why don't we have an academy (like West Point, Annapolis) for politicians, with an honor code and everything, so we'd at least have some idea that the ethically-challenged bozos we elect have had at least the rudiments pointed out to them.