I guess if you're a developer and you just picked up some laptop pre-loaded with Ubuntu and you've never used the command line in your life, it would be better for you to download some file with metadata for apt to consume, and a default file association that gives you a GUI prompt asking you if you want to add the repository. It is kinda lame that Ubuntu doesn't have that. (openSUSE does have GUI facilities for adding repositories, although it's been a long time since I've used them. I wonder if Fedora has something like that, too.)

If you're using Docker to develop applications for Linux servers, the bash builtin `echo` and `tee` are probably among the absolute minimum basics of the command line you ought to learn ASAP. And if you're gonna run Ubuntu at all, the format and use of `/etc/apt/sources.list.d/*` is part of your absolute minimum curriculum, too. I don't think the confusion of folks who are unwilling to do those things is a huge problem in this specific use case.

But you are right in general: it's unusual among desktop operating systems that in the Linux world, users are expected to know about how the configuration for the system is stored. And while I don't think that's necessarily a problem, it would be better if for extremely common use cases (like adding an external software source), users could always use tools (including command-line tools!) that didn't confront them with implementation details such as configuration file paths or lines to be appended to them and instead summarized what was to be done in human terms and asked them if they wanted to do it.

The Debian-based tooling is especially weak here, and especially at the moment, since `apt-key` has been deprecated for security reasons but there's no convenient tooling to replace it at the moment. :-\