The same reasons that advocate an amphibious battalion, can advocate to support with some jets. Similarly for sea level flights, extraranged air interdiction, imagine you have something on the radar and want to know what is etc.. what i mean is that if you have jets you will use them, they are practically useful. All related to their speed and range. Speed is important.The only people who advocate a carrier are those who want one. As I noted earlier, Australia really doesn't NEED a light carrier... A carrier is a red herring... A false dream...
Other thing is your list of priorities, you might want to spend money in more subs rathen than a carrier, but as said, if you have in the paper that you have to buy a sealifht ship (and can buy one that is carrier also), and you have to buy F35 (a,b,c´s) and the difference is 1000 kms of range and some bombs payload, and the real important thing about F35 is the stealth and electronics (that is why it is so expensive) and you have that also in F35b. And you have a refuelling airplane tankers fleet so that the difference in range between a´s and b´s is not importante because because you adapt your tankers contact. And buying the b´s finallly.
So you don´t come out of your budget that was initially for sealift and a´s, and end up with carrier of group of 3 Lhd stronger and more flexible (divide in 2 or 3 groups) than a Nimitz. By the face, ie free.