Limitations of meditation/mindfulness without Vinaya

Some teachers say that the meditation practice without the Vinaya is very limited on its achievments. That is equivalent of saying that lay meditators will have very limited results, even if he/she keeps the 5 precepts. Can anyone explain what is the real difference? What gets limited by not following Vinaya? PS: The teacher was Ajahn Chah, he was talking about retreat, even in retreat the lay person wont get so far because of Vinaya, there is only so much a lay men can develop in meditation (even in a retreat).