"In the 1980s, the social and political philosopher Jon Elster brilliantly generalized the idea of adaptive preference in terms of the complementary phenomena of "sour grapes" and "sweet lemons": We tend to downgrade the value of previously desired outcomes as their realization becomes less likely and upgrade the value of previously undesired outcomes as their realization becomes more likely."
Its like the shifting baseline effect. Each generation thinks there's a lot of fish in the harbor because they never saw how mush there used to be.