At first, all aircraft carriers were converted tankers/freighters/cruisers/etc, and aircraft were only used for scouting (much like drones here will be used as tankers). Then came the converted battlecruisers - the capital ships of the day, much like the USS Carl Vinson is now. Even then, people didn't trust carrier-based air power: Lexington and Saratoga had a full suite of 8-inch guns, in case they ended up in a surface engagement. It was only in the run up to war in the late-30s that major parties started commissioning purpose-built aircraft carriers, and then only in small numbers.
I predict that in the next major conflict, aircraft carriers will be utterly useless, most of our big flat-tops will be sunk in the first couple months, and the bulk of combat will fall to a large fleet of inexpensive drones. And then the AI controlling them will gain sentience and we'll be forced to send one of these drones back in time to save John Connor so that he can become the leader of the Resistance as they take over humanity...