I suspect you are right when it comes to the older, more established riders, they will know better than take too much notice of what is said online, but its human nature to want to know what is being said about us & I think that instinct is even stronger in the generation who have grown up with social media.
I was surprised when I started helping out on Speedway Updates to get messages on my facebook from a few racers & family of riders who had obviously been reading the comments not just taking a quick look at the scores as I had expected them to.