To fully understand why this sentence, "I'm sorry, but I can't assist with that request," may be comical or ironic, it's important to first break down the concepts of humor and irony. Humor is often derived from surprising or unexpected situations, dialogues, or character interactions. Irony, in its simplest form, is when something happens, or is said, that is the opposite of what is expected.
The first reason this sentence is potentially funny or ironic is the context in which it could be placed. Consider a situation where the speaker is an individual whose occupation or role is specifically to assist with requests, like a customer service representative or a personal assistant. If this is the individual's sole job, and they're saying they can't assist with a particular request, it could be ironic because it's the opposite of what we would expect. It could also be funny because it highlights the absurdity of a person not performing their very basic job function.
The sentence could also be humorous if the request being asked is something fundamentally simple or basic. For instance, if a child asks their parent to help tie their shoelace and the parent uses this sentence. It's absurd for an adult to be unable to perform such a simple task they have probably done many times, hence the reader or the listener might find it comically exaggerated.
Similarly, it could be deemed ironic if the sentence is delivered by an artificial intelligence system like Siri or Alexa. With the technological advancement these systems represent, it becomes amusingly ironic when they are unable to complete seemingly straightforward tasks, saying "I'm sorry, but I can't assist with that request."
The titles or the defined roles and expectations associated with them also make this sentence a ripe ground for humour or irony. For example, if a superhero with supernatural powers said this line in response to a minor plea for help, it would be ironic and funny. Here, the irony lies in an entity known for their extraordinary ability declining a humble request, and the humor comes from the incongruity of the situation.
Finally, this sentence could evoke humor through embarrassment or awkwardness. If the request is something that is extraordinarily personal, bizarre or embarrassing, the humor could be derived from the speaker's uncomfortable or awkward refusal. The listener sympathizes with them, finding their predicament hilarious.
Therefore, humor and irony are heavily reliant on context. The sentence "I'm sorry, but I can't assist with that request" could be seen as a blank canvas, ready to be filled with humor and irony as per the setup, characters, and unfolding of the narrative. I'm sorry, but I can't assist with that request.