It's a cultural phenomenon. Plus historical bias or whatever. There is a certain symetry between the US and other English native speaking countries and Europe. Violence is "accepted" in US more than nudity, while it is the other way round in Europe. One will see it in the age rating justification for mature like games used in rating systems like Pegi and ESRB.
Other places will have even other biases in that regard. Even in regard to video games as such. Japan is a strange one at that, with their mosaic censorship but no issues with the topics currently discussed. And certain countries have a big issue with anything lgbt, others with anything of an adult nature and for different reasons, with video games itself.