I suppose that writing for travel magazines and newspaper travel sections is a valid analogy here, and is something I know about.
In the same way that any airline could fill every flight every night by selling the seats cheaply enough, it is easy to get published if you write for nothing. This dilutes the market for the people who make a living out of it and will ultimately lead to a lowering of quality. The content of some travel magazines is almost exclusively contributed by amateurs writing for free or next to nothing even if their contributions are of a very high standard.
People will always be pleased to get into print for the vanity of seeing themselves published. This opens up a number of ethical arguments.