In one of E.A.'s videos, he mentions how it is important to speak forth your intentions. If demons can read our minds, then why is that necessary?
Because it’s easier to make a clear statement for a lot of people than it is to hold a consistant thought, for a start; secondly, the use of vibration and sound in magick is found in most cultures, so there may be a genuine significance to it - making the will take its first steps towards manifestation in the physical is my best guess on that.
Even religions have a place for sacred sounds and words, so there seems to be genuine power there.
Lastly, I guess there’s the psychological thing - anyone can idly want something, but being willing to declare out loud that you command reality to bring you it, is a psychologicial step forward, like spoken confession that can be very healing, compared to mentally mulling over how guilty and bad you feel.