Which stimulates player's creativity, and makes the game a unique experience to each player.
But there's a fine line between exploiting this successfully, and relying on it too much - at which point players get bored.
Modern games rely much less on this. At least not for how the environment looks. Instead machine works hard to present a semi-realistic environment. Enough to "suspend disbelief" anyway.
This lowers the bar for casual players to get into a game. But at the same time, makes for a (somewhat) more passive experience. You explore a pre-designed environment vs. create a good part of it yourself.
Exception might be 'builder' style games like survival games, some RTS / RPGs & of course Minecraft.