While the sibling comment regarding better control over memory layout is right, here we mostly talk about scripting a game engine where the performance critical

While the sibling comment regarding better control over memory layout is right, here we mostly talk about scripting a game engine where the performance critical part is largely inside the engine. So the reason is more likely simply “history”. But actually, C# was always meant as a “managed c++” in a way, while Java rather optimizes on the runtime level (which is helped by less control by the developer). Nonetheless, Java is more than fine for game development, besides the obvious Minecraft there are plenty small to big indie games written in Java.