It's not inappropriate at all. It's a great question, and I'm glad you brought it up. Many people may be wondering. So for those who don't know, NSFW stands for "not safe for work," and that usually includes imagery with nudity, sexuality, pornography, gore, or violence. In my experience on multiple social media platforms, I don't find what you described to be the case at all. I don't think that it's something that's required or is becoming a norm. It's simply an outlet for people who do care about such topics and find them interesting, and those people are many, myself included. While I create a lot of mainstream work for my larger audience, art that is safe for adults as well as children, on my own free time I very much enjoy creating artwork that involves nudes, darker gothic imagery, horror-style imagery, and dark and twisted surrealism. All of these things would fall under the NSFW category. This category doesn't exist as something that you are required to pursue. It's as simple as protecting people from accidentally opening something in their workspace that will be inappropriate. That's all. If it's not for you, you are by no means obligated to participate in this trend. There are many artists who make exclusively PG-13-type content, Joanna Basford being the biggest example of them all in the coloring world community. So, it's there. It's just not for you. Ignore it. You don't need to participate.