What is now called channelling was previous called either “spiritualism” or “mediumship”, and “channelers” were called “mediums”. I will substitute the old phrases, for the modern “channelling” verbiage.
Most have read and heard about ascended teachers, although they are usually called ascended masters, or saints, by most people.
Some people think it is better to follow them, or their teachings, because they are higher in consciousness than living teachers. Some even claim they have personal contact with them, and ‘channel’ them.