> According to a quick search, there are 33M "users" of Linux (I suspect that number is way too low). Only 15k have contributed to the kernel. That's an "exploitation" rate of well over 99.9%.
This is very misleading. There is a lot more code than just the kernel for the Linux operating system. If you ran the numbers for a default install of Ubuntu or RHEL that would be far more useful. The Linux kernel requires far deeper skills than a lot of user-and development so it is going to have fewer contributors per year on average.
Source: I am a Linux kernel engineer.