The act of cultivating a lawn was actually first developed to discourage visitors from approaching people’s homes. The idea was that there would be this immense sea of green daggers (this is why they’re called blades of grass) between a potential visitor and your domicile. Unfortunately, ancient botanists never managed to cultivate a form of grass with blades that are sharp enough to penetrate average footwear… or even skin for that matter. In fact, every hybrid that they produced became progressively softer with each generation.
There was one strain that they produced which, while soft, would actively attack people. Unfortunately, that sample of grass killed its researchers and escaped their lab. Now it roams wild across the countryside, waging its own personal battle against all humankind.