That... doesn't exactly make sense, from a marketing standpoint.
If you have products A, B, C, and D, and product B is mentioned in products C and D, then more people will have heard of product B, and product B is more likely to sell.
If you instead meant "Carriers are optional from a gameplay perspective," well, anything is, really. You could choose to play entirely without Carriers at your table. Or without Destroyers. Or without any ships but carriers.