But actually the hypotheses I've seen align more with the original poster's ideas. Plants don't want their leaves eaten. That's why they produce so many secondary chemicals to make leaves taste bitter or hard to digest. Most plants don't even want their fruit eaten actually. A plant has to spend a lot of "evolution points" (to borrow a phrase from TierZoo) to adapt to being able to survive the digestive process of whichever seed disperser it wants to attract.