Is advertising the solution to useless people?

When I say useless people, I do not mean those who are incapable of being productive, but are instead unnecessary.

Let's start with the idea that technology has made humanity more productive. We are so productive that we do not need to work an average of 40 hours a week. Much less would be sufficient for survival or even for a moderate standard of living. We could work 20 hour weeks instead. Or have 50% of the employable population not working and redistribute their wages and production to the unemployed 50%. The latter would clearly cause major social problems.

What about 20 hour weeks? Those would be less efficient. Why educate and train people just as much as currently when each works only half as much? It would be more efficient to go with 50% unemployed and not working.

Neither of these happen.

Instead we have persuasive advertising. This causes people to buy products which cause only marginal increases in happiness. In fact, studies have found that there are very rapid diminishing returns on happiness such that there comes a point when more work for more pay for more material goods results in lower happiness.

Someone makes these products: The excess 50%. That's right, 50% of people are actively employed doing little more than burning oil and making you less happy. BTW, you work more hours to buy their crap.

This leads to the inevitable happiness economics:
1) Work the same amount and get half hour effort taken away. Be angry about this.
2) Work the same amount and waste half your money. Be less happy due to the extra work.
Which of these is worse? And no, 3) kill 50% is not an option because that still leaves an excess 50%. Percentages don't play nicely with mass-murder.
There is always 4) Everyone works 40 hours and we burn off the excess by bombing each other.