I personally use a few AppImages, but want replace them with Flatpaks. Flatpaks have their own issues, and because I did not want to troubleshoot in case I encounter another issue, just carry on using AppImages for these selected applications. Also I was not able to archive Flatpak easily, its very complicated with keys and not. Compared to it, I just have the AppImages included in my regular backup process with regular files.
My point was not if AppImages are useful (they clearly are and I use them), but was talking bout repositories. However after some other replies I thought about it and indeed such a repository makes sense even for AppImages. I personally just don’t have to use them.