Why not sacrifice old battleships against the Dardanelles mines?

If old pre-dreadnoughts were expendable, why did the Allies hesitate after losing some of them in the Dardanelles?

The hulls could be risked, but their large crews could not; added mine protection offered a better way to use the ships aggressively.

Obsolete pre-dreadnoughts could be treated as expendable matériel, but the same label did not apply to the thousands of people serving aboard them. The proposed answer is preparation: sacrifice some speed, add large anti-mine or anti-torpedo bulges, and put the protected old ships at the front. HMS Queen Elizabeth could then remain behind them to provide modern heavy-gun support and counter Goeben if necessary. The exchange adds the human constraint missing from a simple ship-count calculation.