Because a good chunk of people suck at delayed gratification so are incapable of saving money. Even on an average income it's not unfeasible to retire a million

Because a good chunk of people suck at delayed gratification so are incapable of saving money. Even on an average income it's not unfeasible to retire a millionaire if saving a significant percent (and indeed there are people who do this, small businesspeople and tradespeople, the "millionaires next door").