Think about toilet paper.
Aside from a brief period of time in 2020 when it was scarce, toilet paper is something we barely think about. It gets used, then flushed away and forgotten.
Likewise, some will see you as a one and done relationship to be flushed away. Maybe they’ll tell you they only hire from freelance sites that host hundreds, if not thousands, of similar talent. Or maybe they’ll tell you that they pay a below-market rate because there are hundreds, if not thousands, of others who do what you do.
Toilet paper is a commodity. Are you someone else’s toilet paper?