Apparently they get a 10% conversion rate, which marketers think is worth being the worst people in the world.
However, I would be very surprised if the conversion rate of a popup signup sheet is even 2%.
And there is a similar negative conversion effect: If any article asks me to sign up for anything, I stop reading that article immediately, and move on to an article that respects my attention.
Yes, I am in a small minority. But I also share many links with my peeps, and I never share links with popups. I hope that puts pressure on authors to share things freely.