I m sure there are a ton of throwaway emails, names and such. There are a lot of people surfing porn on the web and many remain anonymous. The problems come up when billing is involved, they need to reveal their true identity.
I don't think these people were unable to use any other email address if they were paying members. Unless they linked their bank to their work email?
Quite the contrary. Imagine, as someone mentioned elsewhere in this thread I think, if the adtrackers got hacked. What might it reveal about you?
If someone threatened to email your boss your entire browsing history, how much would you pay to prevent that?
What if it was being sent to you wife? Your mother?
What if it were being broadcast to the world at large?
These hacks are a dime-a-dozen. Everyone sees Ashley Madison hacks or xHamster hacks and thinks, 'well that's not me. I don't go to those sites.' But it very well could be you. Or worse, someone could falsely claim it was you...