The use of an online video would be considerably cheaper than the alternative of renting a place to give a speech. Also, a video would be able to be easily accessible from across the globe almost instantaneously. The politician would also have time to practice and do re-shoots, so mess-ups and interruptions would be nonexistent. They would also be able to include pictures and short videos if it was a video recording that was aired. Another thing to consider is that the message they might want to convey might only be a few minutes long, rendering the renting and use of their chosen place to be a waste. I think this is what you were asking for, but if it is not, I am sorry.