I disagree that the answer is moral and political and that the "ruling class" sat down to decide most people should work bullshit jobs. The phenomenon is more elegantly explained by pure economics: as less time is expended extracting resources and producing things, more energy is absorbed by the zero-sum, gimmicky game of selling and marketing them.
To give credit where it's due, I first saw this credible argument on michaelochurch's (now sadly inactive) blog [1], and he may well have originated it. Here it is, in a better explanation than I could provide:
"The Marketing and Sales Treadmill
In the modern world [...] there are no unexploited resources and no surplus jobs to be had processing those resources. [The worker] needs a job, but their labor is surplus and unnecessary.
[...T]he most common path is that our prospective worker enters the sales and marketing business. [...] Even engineering focused companies like Facebook have more sales people than engineers. [...] So everyone’s energy is focused on imagining some gimmick – a six bladed razor, a beer can that turns blue when [it's] cold, a funny talking gecko – that gives someone a reason to give you money when there is no real differentiation based on product value.
The sales and marketing economy is zero sum. Each business must work harder and harder at new tag lines, gizmos, tricks, and jingles. And when sales guys at the other company work harder, you must work harder too.
Past writers who imagined the future thought that as machines saved our time, we would have more time for leisure. That has not happened. Instead [...] we must work in sales and marketing to convince someone with money to trade cash for our trinket, so that we can have purchasing power to access the natural bounty of the land. [...] The future is here, and it is the sales desk at Dunder Mifflin."
[1] http://intellectual-detox.com/2013/04/14/rent-seeking-econom...