Really, all of them? In the history of the world there has never existed a writer who thought, hey I think I can do that pretty well, I suppose I will give a try and see if I can make money.
There has never been a writer who, writing for love, also thought, hey that is a great idea for a science fiction story, and that magazine is paying for science fiction, I will, in entrepreneurial fashion try to write a story so I can earn money. If it works out really well I could even have a best seller and move out of this garret! Or did this presumed writer just say, nah, screw that, another volume of poetry about dark haired ladies for me!
And of those who write even without monetary recompense, will they publish?
Will they send off to someone their writing and then sit through the editorial process for months, and agree to changes in order to get published?
Will they go through all the various parts of having to sell since they will not be getting paid for what they wrote?
Rhetorically speaking, Anne Frank is a writer who wrote without caring about any of that stuff, but unless the argument is that we should be rounding up people to send to death camps in order to promote better literature I don't really see the point of the argument.
Sure, after Anne Frank died and the war ended and her father had her diary published he went through the whole editing process and doing whatever was needed to spur sales of the book without much interest in benefiting from the copyright, but I sort of feel that he and his daughter may have been something of an outlier in most publication histories, and their story, engaging as it is, may not actually demonstrate so obviously that "writers will write even without monetary recompense"
on edit: The idea that people are "compelled to write" is essentially an idea that writers have some sort of psychological problem, at least a form of neuroticism, the argument that as they will write without compensation and thus there is no reason to compensate them is at its best an argument to take advantage of people with a psychological condition, although, for all the reasons outlined above I think we can see that the argument is completely senseless and flies in the face of logic.
There has been recent discussion of who was America's Homer, and I suggested Mark Twain https://news.ycombinator.com/item?id=48927260 who was a guy who so blindingly obviously wrote for money in almost all cases that it would just be absolutely ludicrous to argue otherwise.
Also, I see I got my downvote, oh noes!