it's because people cannot disassociate their own anti-war views with the benefits of a military career.
That's why i dont confound the military with the political aparatus's directing of said power. Because the military isn't murdering people for no reason - they are following (in the case of the west) a elected official's policy (which you are very welcome to dislike and oppose, as i do as well).
I think most people still are in support of the idea if military service even if that job may entail death.