Why early carrier flight decks had rounded ends

Why did converted carriers begin with rounded flight-deck edges and later receive square ones?

Rounded ends managed airflow, while square ends were simpler, cheaper, and less demanding of skilled labor.

The rounded ends came from early efforts to smooth airflow over carrier decks. Forming those curves took time and skilled shipyard labor, while square edges were simpler to build. Wartime American and British yards had to allocate a small pool of experienced workers across a rapidly expanding shipbuilding program. Spending that scarce labor on curved deck ends was harder to justify when the same workers were needed to form hulls for many other ships.