I received this e-mail today, and I've received similar e-mails before:
Dear Blabla,
We are partnering with William Hill to bring you these great offers! William Hill offers all your favourites - Casino, Roulette, Blackjack, Slots, Poker and more, along with generous jackpots, great bonuses, live 24/7 support and the latest games.
I don't think a payment provider should write their customers e-mails about gambling offers. I never agreed to that when I signed up, and I will certainly not gamble with William Hill.
But I reckon they're making money off it, and that's what they're doing it.