I'm sure plenty of people find value in chapter covers. When I first started my comic, I was against them, but since then I've realized they're a great way to give you're readers a peek into what chapter's going to be about, they work well as a buffer (like breathing room between two chapters), and they can be a lot of fun to make. And while not all of my chapter covers have comments, at least one does, so there's a chance for interaction.
For webcomic creators, the value for chapters covers can be considered variable, but for me, someone who plans on printing in the future, I might as well add them to the experience as I post online. Granted, my comic is in page format.