One of the great things about liberalism is that it allows for more paths for just that pursuit. In tribal society, there was little to no division of labor beyond what was rooted in age and sex. In feudal monarchies and modern totalitarianisms alike, there is division of labor, but it is imposed on people by rulers: "You will be a soldier.” "You will be a fry cook.” "You were born to be a slave or a serf.” In a free society, you have choice. It's not perfect: You can't choose to be a Marine if you do not meet the requirements, but you are free to try.