Are you going to stop in the middle of combat to emplace ear plugs? Do you Stalk an animal in the brush with ear plugs in?
Assuming these are serious rather than rhetorical questions, I believe that combat troops in Iraq and Afghanistan are
issued air-valve type earplugs. I'm sure that other members who have BTDT know more about this than I do, and also have opinions about how well they work. The principle, however, is a good one. And plenty of people who hunt use either the air-valve plugs or the electronic muffs which block impulse noise. Some say the latter give them more ability to track game, not less.
If you look at the hearing protection sticky in the General Discussion forum, you'll find a lengthy discussion of these issues.
And, yeah, as Tuzo noted above, eye protection is just as important, which is why both are mandatory at many ranges.