This thread has quickly veered into the inevitable realm of comparing the Linux environment to Windows and OSX, which with a few reasonable exceptions, has yielded the usual complaints about each in comparison to the others. As I see it, Microsoft and Apple are in the business of selling an environment for the casual computer user, and with some effort do their best to hide the underlying complexity from people who have no interest in computers beyond listening to music, browsing, checking their email, or using whatever applications they need to do their job.
Of course, Linux can do most of these things as well, but makes less effort to hide the complexity underneath, and can quickly becoming confusing to someone who has only used Windows or OSX. This is evidenced by the large number complaints on various Linux forums by new users who are asked to perform some task at the command line or edit a configuration file instead of using their more familiar GUI environment. I see no reason for argument as people use computers for different reasons, and come from different backgrounds and as such, they should use whatever suits them best. There are plenty of intelligent and reasonable people who have no need or interest in learning more about computers than how to operate the applications they use to accomplish a specific task.
Linux can do many of these things, but these people will almost always find the underlying environment getting in their way because they don't care to understand it, or because the Linux equivalent is not what they are accustomed to.
And this is fine.
As others have mentioned, Linux is simply a kernel around which have grown a large body of specialized applications, frameworks and toolkits, and as such can be used to design a variety of systems for a variety of purposes. Almost by definition it is primarily for those of a technical inclination, who do not mind or even enjoy learning about computers, and what it is possible to do with them. There is little reason to recommend Linux to the more casual computer user, especially as it is almost always done with no care for what they actually want, and is largely out of the personal bias of those recommending it.
Linux is based on a community of developers largely working in their own time and on projects they have personal use for or interest in and they cannot be forced to design or agree upon "a single API" as some have suggested. Of course, there is nothing stopping a team from creating a Linux distribution targeted for the casual user, but then what is the compelling reason to switch, given that there are at least two separate and well-funded environments with this purpose already in mind? Such an environment would, by necessity have to leave out many of the compelling benefits of Linux that I and many others have come to enjoy.
I do not particularly care if Chrome is ever ported to a particular Linux distribution, and if they do adhere to their pretence of open standards, there is nothing preventing someone so inclined in creating a substitute for us as well.