Its not their choice, unless they sell it directly on itch or something, as Steam itself blocks such games from being bought in germany due to the german government wanting to protect underage germans.
https://www.theouterhaven.net/2020/12/steam-region-blocks-adult-only-games-in-ge...
https://steamcommunity.com/discussions/forum/10/1753525962484005680/?ctp=3