I'll bite. Visually blocking text vs video. Either requires a click (or long wait) to get to the content. What is different?

In fact, there's often less waiting with overlays on top of text content.

The difference is how advertising has been done traditionally. Think about TV vs. print. Advertisements need to be interspersed in both mediums, but how it is accomplished is different based on the medium. Why would it be different just because we now consume both on a different platform?