And even out of the majority of people who will say, “yes, they’ll cook at home to save $10K,” only a small percent of those will actually do so.
Even then, it won't save them the money. Like anything else, if you want to save the money - you have to move it out of your regularly accessed account, and put it somewhere else, ideally an account you can't withdraw as easily from.
So - when you cook for your family to save the money - you need to then (immediately) move the money you would normally spend for dinner (perhaps minus the amount for ingredients, time, and power - if you feel it necessary) over to that other account.
But most people never do that, I'd wager.
Instead, that extra money stays in their primary account, which they then likely spend on something else. So their savings continue to be zero (or likely less), and they continue to wonder where their money goes...