Do you know that advertisement could also be a form of hypnosis? It is.
Some advertisements use flash eg flashing their brand image that we may think is nothing unusual but can have an effect on our mind.
The repeat flashing is to appeal to our subconscious mind so thatt we receive the message at a subconscious level. This is similar to suggestions made to a hypnotized person at a subsconscious level and there could be some unconscious responses to the suggestions from that person.