HMS Eskimo provides the visual example for why the class did not receive fully enclosed turrets. Within the available tonnage, a turret would have provided little more than weather protection while consuming working space. It might also have contained the effects of a penetrating shell and made damage to the crew and mechanism more certain. A shielded mount left more room for the gun crew, allowed easier handling, and concentrated thicker metal in the frontal shield. Any penetrating hit remained dangerous, but the more open arrangement offered blast a better chance to dissipate away from the crew.
Notable Point · 25:43-27:18
Why the Tribals used gun shields rather than turrets
The Tribal’s shielded gun mount was a weight-and-space decision: an imperfect turret could add little protection while constraining crews and amplifying damage from a hit.