That's backwards. Do you think these companies are actually willing to negotiate deals with each artist, content creator, website, and code repository? The scale of that alone would sink their business, not to mention the cost.
Worst case scenario - you're right, they're willing to go through that and the authors actually get paid something rather than nothing.
1) That only applies to images, and crucially 2) content on those websites is published under various licenses that often require attribution, payment, or stipulate non-commercial use.
Worst case scenario - you're right, they're willing to go through that and the authors actually get paid something rather than nothing.