Of course they work. They also provide terrible UX.

They work in a "quantitative" manner, it will grow your list but many users like me will close the entire tab at lightning speed.

I think they work mostly because of naive users who think they need to enter their email in order to view the actual website.

So, depending on your targets, you can choose to fast grow your list with random and candid users or have a sharper base of people actually interested in your content.