To my knowledge, they are exempted from that in most other countries. In Australia that is the case, and in New Zealand, and in a number of other cases.
I think from a consumer's point of view, when you're going to give $100 to a charity of your choice, you think that all $100 is going to the charity, whereas in effect a percentage, 2%, 3%, 4%, or 5%, is actually going for the management of the transaction.