tldr: Financial transactions for porn suffer VERY high cashback rates so traditional payment operators do NOT like them because they become expensive to them VERY quickly.
So, he does not trust third-parties with his banking details,
but uses a third-party to send emails with a complete detail of his account to an email-server (which might or might not be run by a third party).
The logic is lost on me.
Furthermore, the e-mails are sent in clear-text and readable by any endpoint on the way transporting the e-mail to its destination. It's akin to sending your information back to yourself by post card rather than stored in a file with a third-party.
The alert emails do not contain “detail of [my] account,” only the last 4 digits of my account (for Chase). Even if someone were to intercept those emails, they couldn't do much with them.
If you go read the Legend Mode, you'll find mentions of Doomdice and you can look up quickly what happened in 1387.
Everything you find on artwork, is either related to the preferences of the dwarf who created the item, or to some of their known history.
tldr: Financial transactions for porn suffer VERY high cashback rates so traditional payment operators do NOT like them because they become expensive to them VERY quickly.