There are some sources that claim that medieval peasants in agricultural economy worked around 6 hours a day, and it was less than is standard today in the developed world.

Seeking leisure is a human nature, true. But maybe also human nature is to compete for resources, get more for your family, and make yourself more attractive to the other sex, even if that means working harder. If the alternative is unemployment, this may drive people to work in (or even create) services that they know are not really that useful.