Why France did not start with a civilian training carrier

Why did France not convert a large civilian ship into a noncombat training carrier?

France already had a battleship hull available and followed the conversion path used by other carrier navies, even though that choice consumed scarce treaty tonnage.

Bearn's conversion looked conventional because Britain and the United States were converting capital ships and Japan also planned to do so. France therefore treated its available Normandie-class hull as the natural starting point. The choice consumed a large share of a French carrier allowance already smaller than those of the leading carrier powers. A cheaper training conversion might have taught basic flight operations, but French planners selected the capital-ship conversion instead.