Why Courageous and Glorious were not modernised like Akagi and Kaga

Why were Courageous and Glorious not modernised as extensively as Akagi and Kaga?

They were treated as experimental carriers intended for replacement, so Britain put less emphasis on extensive rebuilding.

Britain entered the 1920s and 1930s with more carriers than any other navy, but most were treated as experimental ships. Their launch dates and experimental status gave Britain freedom to replace them. British planners expected to build later carriers after working out what they wanted from the type. That replacement strategy helps explain why Courageous and Glorious did not receive the same investment in modernisation as Akagi and Kaga.