Earned wealth becomes inherited wealth because it has been preserved by its earners throughout their lifetime. That is often not easy to do. People with children ‘decummulate’ wealth faster than people without children, first of all (for obvious reasons), and studies show that people intending to bequeath wealth to their children conscientiously spend 25% less on consumer expenditures than most people — precisely to be able to leave something behind for their children — even while they have higher expenses.
In other words, any wealth, whether inherited or otherwise, only stays in a household because of deliberate choices, lifestyles, and disciplined management of one’s finances. No one should really need to be told this if they have ever had, saved, or lost money. Wealth and assets are not static.