[asadotzler]

Same reason you can't sell your organs or sell your physical freedom / time in prison (falsely admit guilt because someone paid you to do so in order for them to avoid prison) or even end your own life. The country you live has citizens who have banded together to created laws and regulations that say these various freedom-y things, if engaged in at scale by people who might have individual reason themselves to do it, are considered harmful to society and so prohibited.