Well, most average Americans do not have infinite options. So when options are limited, you take whatever pays the bills, even if you don't love it. Folks on this board are smarter than average, better educated than average, had a lot more breaks than the average American, and so simply have more options, and there is no need to settle. Additionally, most average Americans will not enter fields which will require substantial years of training, and then have fairly long work hours, so the expectation to like their job is not as pressing. The average American would define his life as what happens outside of work, whereas the average professional would probably do the opposite.
If you have the breaks and ability to become a professional, then you have the opportunity to find a career you will enjoy. If that's dentistry, then super. If not, then get back in the hole and keep digging for something you like better. The notion that "everybody hates their job" and "plenty of people do work just for the paycheck" is the battlecry of the defeated, and doesn't apply when you have better control of your destiny and choices, as most on this board do.