Navy naturally gravitates towards large, multi purpose systems. It's slow and expensive to haul crew a long way, and to protect them you need everything you can put on there. So there's entry cost to building a platform, it has to come with space and logistics infra for humans, must come with self defence, etc. And the bigger ship you make, the more you want to load it to benefit more from it since you move it such long distances at great cost. Army is the opposite, they prefer to divide into multiple small pieces and be harder to take down multiple capabilities with one hit. Navy would do it if it was feasible but it simply goes against the nature of naval operation. A dedicated usv ship is kind of like the middle road, but it has to be seen if it brings more problem than it solves. Aircraft carriers are large, vulnerable platforms loaded with high value targets, and they are used despite that and protectes by large groups because the benefit outweighs the negatives, addes air power is simply too big a game changer if you can handle the cost. USV carrier has the negatives of other carriers but only a small portion of the benefit. So if we are gonna have USV ships, multiple small csrriers that carry 5-6 or maybe 10 at best are more doable. But then if you can carry 3-4 of them with destroyer and don't need extra ships, why risk it?