I remember that I was a kid when I read the news on Slashdot that the Linux desktop experience was going to be basically a competition between Gnome and KDE.
At that moment I knew that Linux would never win on the desktop. All those wasted developer hours.
I am still heartbroken to the day. In capitalism, competition benefits the user, even if the products are virtually identical, because then they compete on price. In the free software world, competition of two indistinguishable products actively harms the user.
The thing is, however, that GNOME and KDE are not indistinguishable - they each have very different goals, ideas on how the desktop should be, how to design applications and UI, what sort of technologies to use and develop, etc and all these end up making two very different desktop environments. As a result, they (and other DEs and WMs, of course) cater to different users and while there are some users that can use both (and all, or at least most of the other DEs/WMs) this sort of "competition" helps the users who align more with what each DE (and WM) provides. In other words, they provide options.
There are people who prefer GNOME over KDE, would you force those people to use KDE? There are people who prefer KDE over GNOME, would you force those people to use GNOME? There are people who prefer Window Maker over any desktop environment, would you force them to use KDE or GNOME? There are people who prefer i3 over any DE or WM that uses an overlapping window UI paradigm, would you force them to use KDE or GNOME or Window Maker?
If you did so, you'd be making their experience with their computers worse - you'd be acting against their choices. If people didn't value having options, they'd flock to a single desktop environment (or WM) and the rest would be a mere curiosity at most. But this doesn't happen.
And of course what Slashdot predicted didn't happen either: in addition to GNOME and KDE we also have MATE, XFCE, Budgie, Pantheon, Enlightenment, Cinnamon, LXDE/LXQt and a TON of standalone window managers to choose from - we even got the rising popularity of tiled window managers, which was certainly not a thing back when KDE and GNOME were new.
Of course, they have different goals, they're using different frameworks and so on. But ask yourself this. If the average Windows user had a choice of two different desktop environments, would they be more likely to be thankful for having a choice, or is it more likely that they would be confused?
Windows and Mac OS X don't allow much customization. Not because Microsoft and Apple are lazy, but because they want the average user to be able to pick up any Windows PC or Mac and be immediately familiar with how to use it.
If we didn't have the Gnome and KDE wars, we would have likely ended with a "standard" Linux desktop.
Considering the popularity of tools like Classic Shell, how much people despite major changes to the Windows UI and even to the lengths some people went to make the classic theme usable on Windows 8 and 10... yes, i'm 100% certain that there would be a lot of users thankful for having a choice.
At that moment I knew that Linux would never win on the desktop. All those wasted developer hours.
I am still heartbroken to the day. In capitalism, competition benefits the user, even if the products are virtually identical, because then they compete on price. In the free software world, competition of two indistinguishable products actively harms the user.