The main reason is that all mining areas are short of people and want to recruit people to dig mines. Traditional migrant workers are all skaters. If they are too tired, they will resign. Strike if you have nothing to do, get a raise and muddle along. Only college students are the most obedient. If there is nothing to scare the leader, he will not dare to quit; It's fun to give a little profit once in a while.
Generally, when we go to the mine, we are all coolies, which is too much for most people. Drilling, grouting (water injection), carrying support (100 kg) and so on. These jobs will last for 4-5 years, and there will be opportunities for promotion after a few years. If you are lucky enough to persist for so long and spend enough money and gifts, you can be promoted to a small leader and you can work in the office. However, if you don't stand on the right side (understand yourself) and don't give money, then you will be a miner all your life.