My only thought for why US might be different is this. In some other countries(e.g. Russia), being in the military carries a good salary and a lot of economic/financial perks that you would not get as a civilian. In contrast, in US, someone as multi-talented as a Navy SEAL, for example, would probably be much better off financially/economically as a civilian than in the military.
My thinking, therefore, was that many people are in the military for non-financial/economic reasons such as patriotism - ergo they are more honorable.... Not completely logical, but...
Cheers,
Kathy