Back in the old days it was the requirement to ship thru Panama. And of course speed, with e.g. the Essex having a fineness ratio of around 9 to 1. And with the introduction of deck edge lifts they mounted the lifts in a way that the didn’t protrude into the hangar space. The new Ford class for example is down to 7.7 to 1, and that’s already pretty plump for a fast ship. Certain seakeeping features also don’t improve when going for a lower fineness ratio. The only way to get a wider hangar deck would be a multihull design. If you “taper out” the hull right from the water line, you’ll get all kind of nasty effects in heavy weather and during harder maneuvers.