Well most animals like human food, more than plants even. Like bears for example. When a bear eats human food, that bear has to be put down, because it will refuse to fend for itself any longer, and will immediately go straight for any human food it smells, thus not only creating danger for humans, but putting itself in danger too. The thing is, people know how to create food. We grow crops, mill grain, milk cows, cook with fire, and animals just don't know how to do these things (and much MUCH more). Most animals eat what is most accessible to them. For example, did you know Pandas are actually carnivores? They're just very very slow, and bamboo is the thing that is most abundant around them, so that's what they eat. They're not even omnivores, they just eat the bamboo because it's there, and it's nutritious. Furthermore, the bamboo shoots usually have water in them, saving pandas a trip to a river or such to drink. Not to mention there are commonly small animals such as rats inside some of the shoots, thus the pandas get some delicious delicious meat. When a panda comes across a deer or some other form of prey, they will pursue, however, as I said, they're very very slow, so they don't get their prey all the time. The point is, animals eat what they can.