As an American, I find it common that the phrase "hero" is something used a lot to describe those who enlist in the military.
I find that although there are definitely some troops who do heroic things, we should not simply throw the term "hero" around as some sort of umbrella term for those who enlist.
Obviously, there are some circumstances in which a soldier does something "heroic" and worthy of praise.
I would say throwing yourself on a grenade to protect the others around you is definitely worthy of the term.
However, there are many who enlist that never see a day of physical combat in their lives.
To use the term "hero" to describe all people who serve is detracting from the accomplishments of those who really deserve it.
Also, using a word with such a powerful, positive connotation for all those of a particular profession is a bad idea because, although it's not fun to think about, some troops are just bad people.
Enlisting doesn't give you a clean slate and a pure soul. Just like every other profession, those who are in the military are capable of doing both bad and good things.
For example, there have been many cases of sexual assault within the institution.
To say/act as if those who serve are immediately heroic individuals is to erase the crimes committed by these individuals as well as the experiences of the victims.
Immediately assuming someone who has enlisted is worthy of such a title is toxic, as it perpetuates the idea that these individuals are somehow "above" the normal citizen,
and that they are incapable of making mistakes and/or immoral decisions.
It makes it seem at though someone who has served is more than what they are, a human being capable of both right and wrong.