Many of the videos that SC removed were high definition. I'm not sure why you think they were decades-old and grainy quality. Maybe that would apply for the first couple of years, but 10 years ago, SC was releasing videos with Stu and Abe and Brandon in high-def and all of those videos are gone.
Also, it is interesting that you bring up CF and Chaosmen. CF has not deleted thousands of videos from their archives. As far as I know, they removed a handful of videos for various reasons (I think one model committed suicide, another was killed), but the vast majority of their content is still online as opposed to SC. I don't follow Chaosmen as closely, but I can still search and find videos from 10-15 years ago on the site, so it doesn't look like they have removed much.
Furthermore, both CF and Chaosmen have gone back to remaster their old videos in higher quality formats, so they clearly understand the value of their back catalogue. They keep the old videos because they know they can use them to make money. That's a strong argument for why SC would keep their videos unless they were forced to remove them.