Who told you that ?
What makes you think developers buy others peoples software ?
This is like saying to Henry Ford, would you buy a Mitsubishi ?
Of course I do.
No matter how skilled I am, there is always someone else who knows things and startegies that I dont know.
yes of course
no body can know or do everything
In addition, you can see more developers in Freelance service are experts and have done more jobs for more customers, but also provide some jobs to another developers as customers...