For me, carriers are the damage dealers/back bone of my fleet no matter the faction i am playing. Most carriers will get you two or three spawns of each unit they carry, this means you can endure in battles for a lot longer and at less cost than spamming individual units. Early game, your bombers on the carriers are going to be the reason you deal any damage without taking substantial losses every battle. You cannot afford to be losing several units every battle until late game, especially for the empire's start.

This isn't always the case though; specifically with Golans, Command Relay Weapons, and other mega bases/threats (more of a 3/3.5 thing, since the reapers are a ♥♥♥♥♥ to deal with). A ship is a big target for these bases and often will mean losing several before they are dispatched with. The command relay's weapon is nothing to scoff at and WILL destroy fleets if you just rush in without destroying it first. Their weakness is fighters/bombers/gunships, as they are two small to hit and are necessary for laying the groundwork of the rest of the assault. In these instances, you are better off having huge stacks of fighters/bombers than you are a mass of vulnerable carriers.