Unless you already have a family to care for, or can't afford to stop working for 3 years to take classes, or can't afford health insurance, or any of a million

Unless you already have a family to care for, or can't afford to stop working for 3 years to take classes, or can't afford health insurance, or any of a million other reasons that life may not be as simple as you make it out. If everyone joined the trades, the supply of trade workers would increase and their hourly wages would go down.