Building a custom rig can be a rewarding and fulfilling experience; however, as Gigabyte asserts, it can get frustrating, especially when it comes to fitting things (mostly cables) around other things. The OEM has launched the new AORUS Project Stealth, a PC that requires assembly rather than building, as a new solution to these potential issues.
https://www.notebookcheck.net/Gigabyte-AORUS-Project-Stealth-launches-to-make-PC-building-easier.621526.0.html
Running cables cleanly is not *that* hard, and it will still need to be done for certain peripherals (HDDS, ODDs, fans, etc). If somebody really wants that badly to avoid doing it that they're going to look at something like this, there's not that much of a leap to just going to a fully built system, where they will have more choices. To each their own, and if someone finds they prefer this route because it's a little easier then that's good I guess, but anyone who is truly interested in building their own computer should do it 100%, as it's really not that difficult and it gives a great sense of satisfaction. The most important thing is to choose a good case that allows for everything you need with adequate space and good cable management.