The kernel running within Android is meaningless. It's not the GUI or the runtime. It performs commodity functions. It's like saying that PEX has 50% of all indoor plumbing share. It doesn't provide any distinguishing, features and the user doesn't care about it. It's cheap, that's its value.
I would agree that the average consumer does not really need to concern themselves with what kernel their operating system. For developers though it does mean that you know your code is written for linux then you know it will work on any operating system using the linux kernel. You can even take your compiled library and reuse it between the operating systems. For people who care about the success of the Linux kernel then keeping track of its market share is nice to know.
