Barricades are used to protect turrents and other things. Both the Rebellion, Pirates, and the Empire used Barricades. Barricades could be destroyed so that the attacker could destroy what was behind it. An example 1 squad of stormtroopers are trying to destroy a anti-vehicle turrrent so that AT-STs can move forward but it is behind a barricade the stormtroopers could die because of having to destroy the barricade unless with bonuses or upgrade or taking cover and so on.