Not everything actually requires a GUI, obviously. But anything that requires configuration, especially for controlling a hardware device, should have a fully functional GUI. I know Linux is all about being in control, and users should not be afraid to use the command line, but if you have to learn another bespoke command syntax and the location and structure of the related configuration files just to get something basic to work then the developer has frankly half arsed it. Developers need to provide GUI's so that their software can be used by as many people as possible. GUI's use a common language that everyone understands (is something on or off, what numeric values are allowed, what do the options mean).
Every 12 to 18 months I make an effort to switch to Linux. Right now I'm using Archlinux, and it has been a successful trip so far, except my audio is screwed, I can't use my capture card at all, I had issues with my dual displays at the start, and the is no easy way to configure my AMD graphics card for over clocking or well anything basic at all.
I'm not looking for a windows clone, I love that I can choose different desktop environments and theme many of them to death. I even like the fact there are so many distros. Choice is a big part of linux, but there is clearly a desire to get more people moving away from Windows and until that path is 95% seamless most people just won't. Right now I think Linux is 75% to 85% seamless depending on the use case and distro but adding more GUI front ends would, imho, push that well into the 90% zone.
GUI is not a dirty word, it is what makes using a new OS possible for more people.
EDIT: Good conversation all. This is genuinely not intended to be a troll post, I just feel it is good to share experiences especially on the frustations that arise from move between OSes.
Does it need to?
I'm fine with Linux, it works for me and I couldn't care less if it doesn't become mainstream, especially if opening to a wider audience means altering the status quo that makes the OS great for people like me.
I don't want a GUI if that entails sacrificing the CLI, you can look at the Flatpak CLI if you want an example: they went all-in with the graphical stores and the command line is neglected.
There are a non-insignificant number of people who want it to be, and frankly it would be good to have the competition in the market space if only to keep the other players honest.
Almost any discussion about another popular OS has a few token “switch to Linux” comments. I see people often using the phrase “The Year of Linux” after that other OS does something unfavorable in hopes to see a massive migration.
So there’s a desire for it to become popular. Maybe it will never replace that other OS, but that doesn’t mean it can’t compete for the desktop OS space.