Most of the person who claims they are contented with what they are doing aren't actually, if they were it can be felt by ourselves so let's take someone who is doing business and they aren't making any progress at all for years but not into any debt then they are not reached the actual potential or doing the wrong business so it can never be profitable in the future.
Whereas the most successful individuals keep showing the progress but they don't change their behaviour much and that is what we can say they are satisfied with what they are doing.
I think it all depends on what comes with the higher level of success. Lets assume that you are a manager at some company, just a manager but not the CEO, you would make a lot less money is that true? But, depending on the size of the company you would still make decent money, not wealthy and going on world tour with your 100 foot long yacth, but it is still better than 7+ billion people in the world (again depending on the size of the company).
Now let's compare that to the CEO, much richer, probably makes millions a year, never need money ever again, and probably works 20 hours a day constantly talking to people. That's what being a CEO means, talking to people all day, you do not do much manual work, but you talk 20 hours a day. I personally wouldn't want that, never wanted it, never will. That's a terrible job, obviously if you offer me 500 bucks per month vs 5 million, I will pick 5 million, but if you offer me 500k vs 5 million, I would pick 500k any day of the week, easy choice.