> Nobody wants their credit card company to know they're looking at porn (as though they care),
There's an interesting and testable hypothesis hiding behind that offhand remark: is there a legal market for information about who buys porn? Are people who buy porn differently creditworthy than people who don't? For example, maybe they have more money (more creditworthy), or poorer impulse control (less creditworthy), or less intelligence (makes it harder for them to pay but also harder to declare bankruptcy, dispute collections, etc.). Maybe there are other customers who would be interested in this data as well: health insurers, or auto insurers, or private investigators, or political or religious opponents. Or, obviously, competing porn merchants, who would love to have a list of leads who are already known to be willing to spend money on porn.
I have this vague memory of an article about how it turned out that people who bought "responsible" products like, I forget, in-wall house insulation or vinyl siding, were much more likely to pay their debts than people who spent money in strip clubs --- even when they were matched for income, age, and gender. Unfortunately my vague memory is not enough to retrieve this from a search engine.