I think the 'agent' trick comes from an adversarial relationship between the caller and the IVR. Properly implemented (this is rare), an IVR should help to collect structured data and save time on the call. If all the users know how to circumvent the IVR, because they think it's a waste of time, you start getting counter-measures to force the user through the expected workflow. Even if it was a well-done IVR, you probably hate IVRs so much that you never want to use one.

It's sort of like if you walked in a McDonalds and started yelling 'Big Mac'. You would eventually get a hamburger, but there's a system in place to get your product to you in a way that is theoretically a good balance between you and the business. If the system is working properly, queuing and ordering will be faster than screaming until you get what you want.