You are fully welcome to contribute. CM isn't a commercial product, it lives because of its volunteers.
You don't need to be a coder to help out. You can help out with documentation, helping people in the #cyanogenmod IRC channel, etc. These jobs free up CM developer time so they can work on code.
It would be in manufacturers interest to sponsor CM. It may even work out cheaper that maintaining their possibly less-competent/more-expensive in house teams.
You're likely under the mistaken assumption that the customer in this equation is the consumer, but you would be incorrect. The customer in this equation are the carriers. And CM doesn't really benefit them.
You don't need to be a coder to help out. You can help out with documentation, helping people in the #cyanogenmod IRC channel, etc. These jobs free up CM developer time so they can work on code.