Agreed.
Getting good bike pics / video is so much harder than skiing. With skiing, it's so much easier to get to some awesome vantage point that shows the scale of some feature, or is scenic, or is just a rad pow shot. With biking, there's always a tree in the way of the perfect angle, and the rider is constrained by the trail so you can't just tell them to ride 50 feet to the right so they're in the sun instead of a shadow, and it's almost impossible to find a perspective on any given feature that conveys steepness or scale.
Which still doesn't answer the question as to why people want to watch some hack flounder his way down a trail. Especially when there's soooo much professionally produced bike content these days that's infinitely more watchable.