Why Tribal destroyers kept torpedoes

Were eight-gun Tribal-class destroyer designs considered?

Yes, but the designers preferred extra torpedoes because the 4.5-inch guns were adequate and torpedoes provided the heavier blow against large ships.

An eight-gun arrangement was considered for the Tribal-class destroyer design. The existing dual-purpose 4.5-inch battery was judged sufficient for the gun role. Keeping torpedoes preserved a weapon capable of delivering a much heavier blow against large ships than the guns alone. The choice balanced sustained gunfire against the concentrated anti-ship power of torpedoes.