Why 1930s carrier air groups divided missions

Why did fighters, scouts, dive bombers, and torpedo bombers become the standard carrier air group?

Their roles complemented one another, although American and British navies assigned scouting to different aircraft types.

The fighter, scout, dive-bomber, and torpedo-bomber roles gave a carrier air group aircraft for different tasks. Navies combined those roles differently. American practice commonly paired scouting with dive bombing, while British practice usually assigned scouting to the torpedo bomber.