First of all, your thread title sounds as if all the recent apps have no screenshots. In fact, I've yet to find one recent app that doesn't have at least one screenshot. I looked at about 10 to 12 of the ones released this past week whose titles were of interest to me. They all had screenshots. After reading your post I randomly chose 10 other apps from the latest batch and they all had screenshots. I'm not saying all apps have them; obviously you've found some or you wouldn't have posted. But my experience shows it's at worst a rare occurrence.
Secondly, I'm pretty sure it's up to the developers to submit the shots. However, perhaps B&N should not allow apps to be made available without shots. I agree that they are very useful. I wouldn't buy an app without a screenshot.
The apps I was looking at were games. Many of the newer ones only have the logo as a picture, but no screenshots. The screenshots ARE available elsewhere on iTunes or other app sites. And many of these are not no-name games, but by EA, Big Fish, Namco, etc.
Just to highlight a few.