In German the Jugendschutzgesetz (JuSchG) prevents certain game titles from being publicly advertised. There are public institutions, that evaluate new game titles in terms of being harmful to minors. If so, it must not be sold, provided or otherwise made accessible to minors. The reasoning behind this is, that certain content may be damaging to young people, which are still developing cognitively and socially. There is an official »List of Media Harmful to Young People«, in Germany usually only called »the index«.

While the general idea behind it is certainly sound, it does have very specific consequences for a title classified as »harmful«, even for proven adults. Game titles found to be harmful may not be advertised and only be sold to people of 18 years and older. But this has the effect, that they are not sold or advertised at all on major game platforms, such as Epic Store, GOG or Steam, when you browse these platforms from Germany. Essentially you will not even find them, even when specifically requesting URLs to existing game pages or entering fitting search terms into the platforms catalog filters. These ttitles basically vanish from these platforms although they do indeed exist and are sold on those platform.

Usually there are however means to circumvent these measures, as these titles are indeed sold to other countries. Geolocation measures and cookies determine whether to show a title to the user, or not. Usually gifting such games is not prevented and VPNs may help to mask the origin of a user. Some platforms, such as GOG specifically state, that this is possible but you are asked explicitly to not use these means.

Also some publishers chose to publish additional versions of games for the German market, that e.g. contains less gore elements, to prevent the title to end up »indexed«. So you might end up finding different versions of the same game in Germany, than in the rest of the world.

For more details on the matter, see https://en.wikipedia.org/wiki/Federal_Department_for_Media_Harmful_to_Young_Persons#The_List_of_Media_Harmful_to_Young_People.