Thank you! To make it even more rewarding for you :) - I remember there was a report mentioning that most of the work on Linux kernel nowadays is done by salaried employees.
Lines of code are of negative value; adding more actively harms the project, all else being equal. Contributions are in terms of what features were puchased with that harm (and some features are harmful in and of themselves, but Linus is pretty good at rejecting those contributions, if not the not-worth-their-loc ones).
Because every company that has libraries, products, stacks, customers using Linux sooner or later runs into issues in Linux, that they can't wait around for someone else to fix.
Big orgs have lots of people just working on Linux full time. They start out fixing one small thing, which then needs to be updated, optimized etc etc and then things snowball.
Yes, I think you're right. In that case, it certainly wasn't the case back when Linux started. Intel and Redhat are the biggest contributors according to the Linux Kernel Development Report from 2017:
Intel 10,833 13.1%
none 6,819 8.2%
Red Hat 5,965 7.2%
So, "none", although it's the second biggest category, only accounts for 8.2% of contributions.
I see, and so you assume that that job would be the contribution.
When I contributed to the kernel (in a rather minor way, I hasten to add), I was competent enough to get a job as a programmer but my job had nothing to do with the kernel. As far as I can remember that was typical for the people who contributed during the first five years or so. I didn't pay much attention after that.
Thank you! To make it even more rewarding for you :) - I remember there was a report mentioning that most of the work on Linux kernel nowadays is done by salaried employees.