I don't think it's that.
I think it's more that there is an over-supply of people who want to be writers, and because they desperately want to be writers, they are prepared to write gratis.
Writers have been told that they have to 'pay their dues,' that they have to find their own readership, that if they try long enough, they will eventually make it - all o those statements false.
So millions of people try their hand at writing. I think it's 85% of Americans who want to be writers.
Commerce has taken advantage of this. Why wouldn't they?
Harlan Ellison sums it up best in the video below.