They want to get rid of all or most code written by the hobbiest programmers from 1990-2013, so they are not able to claim to have code in the linux kernel.
They are doing so by removing all old drivers and old code one by one, replacing it with nothing, or with corporate written code that they own the copyright to.
This is so the original programmers of Linux cannot revoke the license to their needed code, and so they cannot get a job
>Oh you're code is in Linux!
vs
>What" your code was thrown out of Linux?1