True, we are not carnivores. However, we are omnivores. If you look at our teeth, we have molars for chewing up vegetation, but also incisors and canine teeth for biting off bits of meat. Strangely enough, we have also evolved to eat cooked meat, as our teeth are much smaller than other omnivores. Weird huh?
Meat does contain nutrients in a much more easily digestable form than found in plants - Iron being a key example.
I would saw though, that many people who eat meat tend to overdo it - which can lead to health issues. However, vegetarians (in my humble opinion!) tend to be more health conscious anyway. Perhaps this may have something to do with the difference in mortality between the two populations?