Wanting sex is a normal and human desire, and NSFW content is just an expression of that, but without any of the effort or risk of rejection needed to get a sexual partner in real life. Some people like to imagine themselves or their ideal partners in the scenes they view. Some have specific kinks or preferences that are harder to find, thus the need to pay for it. Some have parasocial relationships with the creators.

As for the “nothing new” part, well, you’ve probably eaten your favorite foods hundreds of times in your lifetime without getting tired of them :)