For some peoples, they will choose build their own bitcoin mining because its give bitcoin every month. But before we start build our own mining, we should calculate our cost. Electricity cost is biggest cost and we should compare it with bitcoin price.
The mining of all cryptocurrencies has been decentralized for a long time. This made it possible to attract new miners. But now the situation is changing. People with large capital entered this business and now they are gradually increasing their capacity and replacing small miners. It seems to me that soon this market will be completely monopolized.