I second that about scenery watching. Where else would you get such a tour of the countryside with the historic points mentioned along with exclusive detailed overfly by helicopter where you can see down the chimneys. Some people watch the race because of that, not caring much about bike racing.
I think most of those lining around the roads don't care much about the race either, they come in because of the huplaah, its like a circus came to town thing.
I consider myself quite knowledgeable but also miss some info during races, why this or that is done or not done. But there is that problem of repeating which bores those who watch all races and have heard everything there is to hear...
Also some viewers who have one of those expensive bikes and care for it like for a baby think it is the same for these pro riders. But for them, it is just a tool to do the work with. There was this big mountain climber giving a talk and someone asked him, if he got some piece of equipment he cared for and took along on all those big mountain climbs, like a favorite carabine, to which the reply was that there is no 'private' equipment. Even if it often wasn't left behind on the mountain, everything is thrown together and everybody takes what he needs to take. Except that bikes have to be adjusted to the rider size and comfort.