Galra culture is rather shamelss (why would they be?) and things like public baths and such are common and enjoyed by most. Throk however, it not one of those individual. He is in fact, uncomfortable with bathtubs or the like. Firstly due to the deformity in his chest being a dead give away that he is not the most study person and should someone see it, it would undoubtedly lead to harassment if not more serious confrontations by those that don’t see him as worth of being in the army let alone a high ranking officer.
The secondly reason is one of his earliest memories is that of a male galra (likely his father) trying to drown him in one when he was two year old kit, and it wasn’t even the last time that he’s nearly been killed in the fashion of being submerged.
He’s since taking to either showers or washing with bucket and cloth.