I have not watched a great deal of UFC, but when I did, I don't recall seeing one eye poke,throat strike, or groin shot. Most people can take a punch to the jaw or kick to the leg to bridge the gap. Not many can take blows the the very targets the UFC eliminates. I am not trying to downgrade grappling, but lets keep in mind that the rules make it a sport and not a true fight.
You have to have both if you want to be a good fighter, the pure grappler will almost always beat the pure striker. The pure bred grappplers and strikers rarely make it very far in my opinion.