Shared parts versus a genuinely multirole carrier aircraft

Why was the Blackburn Blackburn not repeated despite its spare-parts commonality with torpedo aircraft?

Because it could only spot and reconnoitre, while scarce carrier spaces favoured aircraft that could also attack with bombs or torpedoes.

The Blackburn Blackburn was intended as a spotting and reconnaissance aircraft with maintenance and spare-parts commonality with frontline torpedo aircraft. Its conspicuous large cabin protected the tables, maps, radio, and navigation equipment required for its specialist mission. Sharing technical support with strike aircraft was logistically attractive, especially aboard a ship with limited stores and maintainers. Yet every carrier air-group position was scarce, and other aircraft could perform some observation work while also carrying bombs or torpedoes. The same pressure for versatility appears in the logic behind a modern type such as the F-35: each embarked aircraft is more valuable when it can perform several missions. The Blackburn Blackburn therefore explains why a genuinely multirole aircraft could be more useful than mere parts commonality.