The video response seems like a good idea if used properly. Unfortunately, many of them are irrelevant to the video they are responding to, and it never seems like there's a reason to watch, and they can be hard to find. YouTube is going to retire these on September 12, and start allowing users to put links in the comments. The video responses have a horrible CTR and YouTube decided there needed to be a change there. I'm not sure how the CTR on comment links are going to be any better (or even if that's the goal), unless they happen to get up-voted a bunch and show up as a top comment, but the change is coming.
Why the Video Response Is on the Way Out
YouTube found that there was a .0004 percent click-through rate on video responses, or 4 out of every million users. This is likely due to a number of factors surrounding irrelevance and the relative difficulty in finding them. Video responses never seem enticing. You could watch a video about antelopes, and there's someone leaving a video response to their cover of a Rihanna song.
This will be something that creators will need to enable on their channel once it becomes a reality. I'm sure this will also be abused, though. How many relevant "responses" are actually going to happen in the comment section anyway? Still, I guess this will be easier for users to navigate, and there will be a little less clutter without the extra thumbnails.
From the YouTube Creator Blog:
In the meantime, you can continue to encourage fans to upload videos with specific titles, hashtags or descriptions (e.g., Video Response To Taylor Swift's Video "22"), so you can find these by searching for them. If you want to highlight them, you can use playlists and channel sections instead of displaying these videos below yours. Any video responses you or your fans have made will still be available and discoverable.
Once considered a powerful way for creators to associate their (relevant) videos with popular videos, video responses had their own little section in the "Playlist and Video Response" section of the first editions of the YouTube Creator Playbook. But "video responses" were lumped in with playlists and even when YouTube wrote about them, they didn't seem like they belonged. So they'll be done in a couple of weeks.