Why were casemate guns still common on cruisers around 1910?
Short answerThey protected crews and allowed relatively light mountings to train quickly before suitable powered turrets offered wider arcs and better magazine access.
NotesThe answer treats casemates as a normal feature of the period, using Olympia as an example. Their protection helped gun crews keep firing. A relatively light mounting could train quickly when a large powered turret was harder to make responsive. Once suitable turrets were available, their wider arcs and direct magazine access offered advantages. The explanation concerns the technologies and duties of the period rather than a claim that one mounting type was always best.