edit: I think the question is relevant, because part of what is going on here is that projects like Ubuntu and GNOME are taking cues from Apple's success
Go KDE.
Like apple did with the iphone?
http://techland.time.com/2013/04/16/ios-vs-android/
Depending on which metric you chose, either iOS or Android is ahead. However, the data is not conclusive enough to warrant your statement. If anything, it seems to be leaning in the opposite direction.
http://www.jdpower.com/content/press-release/upO8vjP/2012-u-...
At any rate, the only reason you need is user choice! User choice is always a valid reason. Removing customization options is rarely the proper thing to do.
Of course, in this case, users still have a choice: they can choose to install another terminal! Which it seems many of them have done.
Allowing people to choose their own fonts can make text less readable. There are only 3 or 4 reasonable choices anyway, so all others should be dropped.
Allowing themes to change window decorations can cause confusion and reduce usability. Let's drop that.
Having more than one window manager available is inefficient and means that more developer time is wasted in duplicative effort. Only one window manager is needed.
Having more than one web browser is inefficient and means duplicated effort. Drop all other browsers.
Having more than one Linux distribution is inefficient.
Having more than one OS is inefficient.
Having more than one system architecture causes needless work.
Supporting any NIC that isn't the best makes the system less efficient. Drop inferior NICs.