Avg home user uses no OC. Of all the 100k's of PCs that are sold, most are bought by businesses and home users. You are talking about a group of people who barely know how to use a PC, let alone OC it. There is a reason why Intel is number one GPU maker.
http://wccftech.com/nvidia-amd-intel-gpu-market-share-q3-2016/
The overall trend of the GPU market share is that NVIDIA, Intel and AMD are the only three companies that dominate this sector. Intel leads with their 70.9% market share
Most people buy a PC, but only use the onboard. And most of the time that's an Intel IGP. OC? Most people don't even know what that is.