BTC was developed by Satoshi as a CPU minable coin with the principle of 'one CPU, one vote'. It remained a CPU only coin for the first few years until eventually it had gained enough notoriety and profitability for people to look in to developing a GPU miner for it and eventually, ASIC miners. Even today there are some new POW algorithms that are launched as CPU only, until a GPU miner is developed.
so he based it off the cpu code. I wonder how satoshi feels about master nodes