Pick any of the following reasons:
1.) Because the purpose of the automated system is to get you to the right person. Those buttons might keep you from getting to, say, billing disputes when you’re calling to add service. Or, if you’re calling regarding a product, to the people handling the right product. My guess is that some of these systems might actually relay to a rep, but most of them probably scan for keywords or something. So. . .entering in that information might save you from having to be transferred later.
2.) Security verification. For complex transactions, they’ll want you to verify with an actual person. This makes it easier to pull the call if there’s a dispute.
3.) Idiots. Half the people screw up their account number. And. . .not all screw ups might lead to “no account found.” You might end up with the wrong account number entirely coming up. Or something on the account on file might be wrong; in that case, having the customer give the information to a human being helps.
4.) The rep might get the information, but may still need to verify it. I work in a financial-based call center. About half the time, the account information pops up on the screen. This allows me to have a decently good idea of where I need to be looking, what systems I need to go into, what pages I need to have up, etc. But. . .I still have to ask the caller for an account number, and am to instruct the caller that the information entered into the system is for routing purposes only (and it is–not all people in the center might serve that particular product).
5.) Some problems ay be able to be solved via an automated system. While this isn’t really an issue where I am, this is an issue when I call customer service for, say, my computer or my router. And if you have to wait less time to get it solved, that’s good for everyone involved.
IME, #2 and #3 are the main reasons, in that order. And that’s for good reason; if something happens and the call has to go to legal, we want to be damn sure that we have our asses covered regarding security. Admittedly, this is less of an issue when you’re calling about your broken iPod. . .but it’s still there.