Swearing is a part of human language and human speech. Most human beings will swear at least under certain circumstances. Nor is swearing a new phenomenon. Most of the swear words we still use today are very old indeed. You can find swearing in the works of Shakespeare, Goethe, Chaucer, etc...
My characters swear, when it makes sense for the character and situation. Some of them swear a lot (and interestingly, my female characters often swear more than the men), some occasionally and some never/hardly ever. Just like real people. I am careful with the big taboo words, i.e. the various racist and homophobic slurs and the c-word. With these words, I carefully weigh whether I really need to use it and also include a "strong language" warning in the blurb. I don't worry about the f-word and the s-word (and don't use a warning either), unless there are multiple instances on every page, in which case I tone it down a little. As for the various religiously tinged swearwords, i.e. profanity in the original sense of the word, those are largely invisible to me, because those terms don't bother anybody in Germany and hardly count as swearing at all.
Like Rosie Scott, I also tend to roll my eyes when there is a situation where the characters would realistically swear and yet for some reason don't or - worse - used defanged swearwords.
"Fiddlesticks", exclaimed Manly McMannerson, the heroic space marine, "Those dastardly aliens have breached our defenses and the darned plasma cannon is out of order."
Honestly, that sort of thing only belongs in parody. I also hate made-up swearwords that are particularly common in science fiction. For starters, it's usually obvious which word the made-up word is supposed to replace (there's a reason they all start with F). And secondly, those made-up swear words sometimes are actual words in another language, which can jolt you out of the story completely.
So yes, there is swearing in my books and my readers don't seem to mind. And those who do mind likely aren't part of my target audience.
I also find it interesting that Americans are much more bothered by swearing than by violence, whereas it's the opposite in Germany.