Why early warships did not begin with torpedo bulges

If mines and torpedoes were known threats, why were First World War ships not designed with anti-torpedo bulges from the start?

Bulges imposed speed, beam, and docking penalties, so new ships generally used internal defenses and received external bulges later when those defenses proved insufficient.

An external bulge can absorb an underwater explosion before it reaches a ship's vital spaces. It also increases beam and drag, reduces speed, and can exclude the vessel from existing dry docks. Designers therefore tried to incorporate torpedo protection inside a new hull when displacement and internal arrangement allowed. Bulges became especially attractive during refits, when an older ship's protection had to be improved without rebuilding the entire hull.