Most of the companies on that list are hardware developers adding drivers for their own hardware, which generally benefits nobody other than their own customers. A five-line fix to scheduler performance is way more valuable to the community at large than ten thousand lines of code to support a 25GbE network card. (The 25GbE driver is hugely valuable to Amazon, though! And, depending on how you look at it, may well have been sponsored by Amazon by being a big customer of Linux in the datacenter.)