I think our navy is mostly designed for prestige too, but it seems like you could use the current carriers to transport like a million disposable drones?
To what end? You can use them as an extremely expensive cargo ship, sure. But if you're talking about launching drones off of our carriers, you have the problem that whatever you are in drone range of is also in drone range of you.
And btw, if you can get a submarince close to your target, torpedoes and missiles are going to be much more effective than drones.
Space is limited on platforms, a submarine might have space for 60 drones or 30 missiles, given the immense cost of the submarine, going with the missiles is the right call.
The trucks launching shaheds that iran is using can fit like 5 such drones, a similar truck could probably fit 2 to 4 cruise missiles the only reason they are using drones is the rapid production and cost associated with drones instead of the cruise missiles.
It may be hard to locate a submarine out in the deep open sea, not so much if they are limited in escape routes. Some $50 microphones in the water will be able to pick up submarine activity and if the sub is in range of sending out drones it is in range of being detected by drones equipped with simple magnetic sensors. And that is assuming they can't put an active bit of sonar on two or three drones and drop them in the sea and triangulate it to within a few hundred feet to start with.
That still doesn't make them easy to take out, but the cost of potentially losing a submarine is so massive that it doesn't make sense to risk them to start with.