I spoke with a criminal lawyer about 6 months back. He is a hobbyist, we have a friend in common, so I sometimes bump into him. He told me when he hobbies, he prefers paying the agency using credit card. When he goes for the visit, he goes cash free.
His line of reasoning is that if he gets arrested, he won't have any cash or a wallet on him. That would make it more difficult for the Crown to prove he is paying for sexual services, because you can't pay for something if you don't have money to purchase that something. I don't know if this logic is iron clad, but it seems sensible on the surface.