I don't think anyone intended to create this shadow economy.
That's one of the conclusions I'm reaching about the economic system in general: much of it isn't so much planned as it just happened (though there have most definitely been very long-lived efforts to influence both how people think about the system and how it functions -- going back to Smith and before).
But I also feel that much of what "just happened" is also less than beneficial through both perverse incentives and externalities.
Your "truly picking up people when convenient for their usual routes" existed for a time in the form of hitchhiking, and survives today in limited forms such as casual carpool arrangements.
Yes I completely agree with you! We plant the seeds of systems, be it legal, educational, political, economic, etc., and then they evolve, grow, and spiral (fueled by their own momentum and interesting side effects) to a state where we often lose control of the system completely, and then have to submit to it, instead of the other way around.
You might enjoy some of Kim Stanley Robinson's talks on YouTube and elsewhere. One point he brings up is the idea that as human systems evolve, they tend to have the elements of the precursor, present, and successor systems in them. So presently, capitalism has elements of its precursor, feudalism, and whatever its successor will be.
With capitalism, we can say that it has very strong residual elements of feudalism. It's as if feudalism liquefied and the basis of power moved from land to money, but with the injustice of the huge hierarchical feudal differences between rich and poor still intact. What is emergent in capitalism is harder to identify, but there may be something to the idea of the global village, also the education of the entire world population, so that everyone knows the world situation and wants justice, that may be leading the way to a more just global society. Seeing and exaggerating these emergent elements is something utopian science fiction tries to do. So the dichotomy is a sort of x/y graph in a thought experiment.
That's one of the conclusions I'm reaching about the economic system in general: much of it isn't so much planned as it just happened (though there have most definitely been very long-lived efforts to influence both how people think about the system and how it functions -- going back to Smith and before).
But I also feel that much of what "just happened" is also less than beneficial through both perverse incentives and externalities.
Your "truly picking up people when convenient for their usual routes" existed for a time in the form of hitchhiking, and survives today in limited forms such as casual carpool arrangements.