There is a high competition for specialised hardware. When Bitcoin started, everyone could mine it on CPU, then GPU, then FPGA and now only an elite can afford the $10K ASIC. The production of the hardware is highly centralised and the people that have access to it are decreasing everyday.
That's partly because we are at a special time in Bitcoin history. It will mature fairly soon (over the next 5 years). ASICs will plateau in power as they catch up with mainstream chip technology. Then they won't be superseded so quickly, so they'll be kept longer. They'll be produced in greater quantities. They'll become cheaper. We'll go back to more people being miners.
But people still have to buy those chips and eventually one company could make them all.
Bitcoin is centralized, it wont be worthless even if it is centralized but let's not act like Bitcoin will be the best coin 5 years from now. I don't think it will because by design Bitcoin isn't easily scalable or flexible.