Sure, the money isn't generating more wealth, but that amount is finite. It's a cushion that should effectively indefinitely and every dollar beyond is vigorously invested. And, should something happen to employment, you use it as a buffer (assuming no severance) and replenish as soon as you're employed again.
I have a friend who helped me get where I am. He makes even more than I do, but financially, I'm more well off than he is because he thinks that every single dollar needs invested -- to the point that despite making the top 2-3% of income for our entire region, he regularly is paying off revolving credit card interest because he isn't equipped to pay a $500 unexpected expense.
Sure, if you invest every single dollar, it's always earning 7-10% on average. But if you have to then pay 20%+ APR on credit cards because you can't handle unexpected expenses, it begs the question whether you're really getting ahead.