Procedural generation for plants is actually pretty common already Most trees you see in video games are from middleware like Realtree
Now suppose I want to take some fruit from the trees. And I want to slice and dice the different fruits. Peeling the skins when appropriate.
Or I want to plant a new tree. Or I want to remove it, with say, a lightsaber.
That's a couple generators more. Now add birds, dogs, insects, moss, moist surfaces, and so on. Hence, my point on needing several generators.
There are lots of things to be improved in games, but what you're describing are improvements to a real life simulation.