Sometimes one can easily get mislead by commit counts as an "index of contribution" to fixing issues within the Linux Kernel. I deal with a lot of gnarly kernel related issues when new kit is being brought into the market and quite a lot of the fixes don't result in kernel commits. For example, identifying BIOS related issues (such as suspend/resume) and getting these fixed in the BIOS can take many hours of debugging and leads to a machine reaching the market which works for kernels all distros. Such a fix does not get measured in the kernel commit logs - and hence it seems no contribution has been made.
I've also worked on tracking down problems in closed source binary drivers where I've identified where and how the problem is occurring and suggesting a fix which ultimately ends up in improving a driver - again another fix that's not apparent in the kernel git commit log.
Don't get me wrong, I don't want to excuse myself from apparent lack of commits I make in the kernel - however I do want to let you know that bugs are being fixed silently in the background which lead to Linux running better on new hardware and it benefits all Linux distros.