With the game in its current form the player can only remove underground walls, not build them.
Having the option to build walls allows for players to adapt and evolve the nest in certain ways. For example, it allows the player to increase the travel distance between the queen and the nest entrance. And the player can fill in small spaces were underground enemies waited to be dug out to complete a fully upgradable chamber.
Placing walls also allows players to block off the nest. A way to combat this could be to make enemies tunnel to the queen should there be no possible path to her.
Simply put, having the option to place walls prevents the need to plan the entire nest at the start.
Having the option to build walls allows for players to adapt and evolve the nest in certain ways. For example, it allows the player to increase the travel distance between the queen and the nest entrance. And the player can fill in small spaces were underground enemies waited to be dug out to complete a fully upgradable chamber.
Placing walls also allows players to block off the nest. A way to combat this could be to make enemies tunnel to the queen should there be no possible path to her.
Simply put, having the option to place walls prevents the need to plan the entire nest at the start.