everything can eat meat raw
but cooking it makes it easier to digest. just like herbivores tend to graze grass and leaves because theyre plentiful, even those without a cecum who just have to kinda live with being shitty at life, but if they got into a grain field theyd go nuts and get way better nutrition, get to spend less time grazing
it's just yknow, without humans to plant and tend for those higher-yield grains, they couldnt exist in nature. they have to be selected, and they require a lot of localized input of water and fertilization, not to mention crop rotation, because of their higher concentrations of broken-down food energy stores.
there's tubers and shit, sure, but how many animals can dig them up?