Why did Dreadnought retain wing turrets?

Why use wing turrets for heavy guns when a centreline arrangement seems more sensible?

Fisher wanted six heavy guns firing forward, reflecting Lissa-era pursuit doctrine and his belief that concentrated bow fire would overwhelm an enemy before it could reply effectively.

Dreadnought's wing turrets reflected the perceived lesson of Lissa and expectations of head-on pursuit or withdrawal. Fisher wanted six 12-inch guns firing forward and estimated that they could deliver three hits in a minute. An opponent with conventional fore-and-aft turrets would have to turn broadside, presenting a larger target, to bring comparable weapons to bear. Fisher later remarked that access to a satisfactory superfiring arrangement would not have removed the wing turrets in his scheme; he would have added another turret to increase the expected hit rate. That tactical arithmetic helps explain a layout that appears inefficient when judged only by later centreline practice.