I strongly suspect that these famous authors can afford it. Plus they are protesting about something that already applies to dozens of people, who aren't famous enough to make a big stink about their character being questioned.
So if I want to be on the preschool committee, even if I never have contact with the children other than to chat to their parents waiting outside, I have to be CRB checked.
I am on the Guides Hut Maintenance committee; that means I occasionally meet with one of the Brown Owls about which Gutter leaks or where to buy printer cartridges. So I now have a CRB check from Guides, too, just because Guides has to do with children.
Honestly, these rich authors are a bunch of whingers. And I do see them as "rich", because a close friend, a published author of many children's books, goes into schools to lead all-day drama workshops. He had to pay for his own CRB check to let him do that work, his main source of income; his books aren't best-sellers. Now, if he were famous enough, he could get paid 3-4x as much just to sit in an assembly for less than an hour, read a few passages and answer a few questions. That would be a dream job for him, low stress, complete doddle, etc.