I never understood what the Rook was supposed to represent. Everything else has a rough analog to actual battle. But castle towers are notable non-mobile.
Originally, the rook symbolized a chariot. The Persian word rokh means chariot, and the corresponding pieces in Oriental chess games such as xiangqi and shogi have names meaning chariot. Persian War Chariots were heavily armoured, carrying a driver and at least one ranged-weapon bearer, such as an archer.
I never understood what the Rook was supposed to represent. Everything else has a rough analog to actual battle. But castle towers are notable non-mobile.
Modern ones are akin to siege towers is my take.