In my experience, ritual is extremely helpful in IM/LoA. I think I hinted at it before in a thread on Intentions where I asked people about the phrases that they include with their Intentions.
Does it help because that's the way the LoA works? I don't think so, but I could be wrong. I think it helps (and it does help tremendously) because of the way the human brain works.
Ritual has two aspects, one seen by the initiates, and one seen by people in the higher degrees. When an initiate sees a ritual, she sees the actions and the symbolism very clearly, after all, she had just been studying that very thing.
When a person who has at least their first degree sees a ritual, though, (hopefully) they start to participate in the ritual from habit, which leaves the body occupied while the mind can work on other things, such as building and focusing energy (which was where I shined) or forming imagery specific to the ritual being formed. Many of us who have worked with IM/LoA know that having clear imagery or a strong emotion are very useful in manifesting, and a ritual is just a tool to bring your mind in tune with what is most effective.
There may be more to it, but I haven't made it past the first degree, and I'm not certain that I will. Ask an Elder, and maybe they'll tell you.
Irregardless of if there is more to it, though, any Elder (who has let their ego go... I've met many who are still very ego-oriented) will tell you that the ritual is a tool, and not the only means... It just happens that the rituals they perform are the ones that they are the most familiar with, which makes those rituals the most effective for them.