Being one of the most powerful tools in the hands of the U.S., aircraft carriers are one of the most ambitious targets of any anti-American country. That’s why they are also some of the most heavily defended assets which does not travel alone (as done by the Chinese trainer Varyag) but alongside a Strike Group (once known as Battle Group) including ships, supporting vessels and a nuclear submarine, whose task is, among the others, to defend the flattops from underwater attacks.
A battle group can be easily seen so what your going to use your subs on lone ranger missions where they will get blasted by enemy submarines because in hostile territory it will be facing more than 1 sub.
And don't you think Iran has got submarines? The Iranians went shopping. Along with some Mig-29s and Su-24s, they acquirred three Russian-built Kilo-class submarines, and, I believe, options on two more. These are diesel-electric boats that the Russsians swore by for shallow-water and coastal operations, claiming that they were quieter than a nuke. These submarines also featured a coating on their hulld that absorbed sonar impulses. The question is, are these boats still serviceable and are the Irnians capable of duplicating the technology.
Those flatops are worth billions of dollars. I would suspect in waters close to Iran they will use as many of their subs as possible. Or did your forget your country is almost at war with Iran?