Back in the day when selling porn as an Independent pornographer was hard. We had to learn fast, what girls could do the job, sold, what they were suitable for, etc. We also had to learn how to shoot porn. Shooting a front cover for a magazine of DVD box cover is a demanding job.
Without those money shots, the video or set are worthless or worth less. The set or video had to include key elements. No matter how good looking the girl was, she had to invoke emotions in the viewer, other than the fact that she's just another naked body doing porn.
The traffic was there as it has always been. The key was conversion and retention. Would the cover shots convert the browser to buy? Would the content please him enough to keep him buying that brand? We know this worked in porn because some sites were streets ahead of the others. Maybe they didn't convert so well for the individual, they had to be making a lot of money to run such an organisation. Even so, some affiliates swore blind micro niche sites that were barely making a profit converted best.
The problem is webmasters took over and traffic became the #1 priority.