The profits are also reinvested. The thing that stops most people is they fact that it takes twenty years or so for this to start showing significant gains.
Compounded interest is a wonderful; thing, the longer one can collect it. Another thing that helps is, as my dad used to say, "Live below your means." Just because you have a dollar does not mean you need to spend it. It was investing as much as I could at any given time in a 401k, and not trying to spend or borrow my way to wealth that enabled me to retire, comfortably, before I was 50 years old.