I can say, with absolute certainty, that is not the norm.
For every sale they make, there are countless others they don't. And they still have to put in the time.
I've gone through many realtors looking for a house, all of them gave me hours of their time and didn't see a penny in return.
That said, I don't think realtors are necessary and we should push the idea that people shouldn't use them unless they think they need to.
A lot of it is an instinctual response.
Hearing 'jews this, jews that' since birth causes people to want to 'fit in' and go along with what everyone else is doing even if they don't understand it.
I was surprised by how much anti-Semitism existed when I went to high school, because I never experienced it before outside of South Park. For everyone else, it was just normal and understood (even if they didn't support it.) It really cemented the idea in my mind that most people do things without thinking just to fit in with others.