Porn.
When I first looked into stable diffusion I wanted to see what people were making with it and there was a few sites that showed stuff people had generated and it was 70% porn 29% high fantasy wallpapers (numbers are illustrative). Recently I've been looking at different text generation inference platforms like tgi and vllm on reddit, and 1 in 5 posts in the localllm subreddits are "What's the best model for erotic role play?"