Straight-up incompetence on the part of the systems integrator or designer. I'm so tired of this shit, especially when entry of an account number is essentially a REQUIREMENT to even get into the system.
Can confirm.
My first ever programming job, 20+ years ago, was doing CTI (Computer Telephony Integration) and call-center integration stuff... basically, building IVR's and integrating them with backend databases and customer support apps. Truth is, there's rarely - if ever - any real technical reason to not have the agent shown the customer's information as soon as they pick up the call. This stuff was all being done decades ago.
As far as I'm concerned, it's either "straight up incompetence" or "straight up laziness" or some variation on that theme.
There are lots of technical reasons why they might not see it, but it all comes down to someone not caring enough when deploying (or updating) these solutions - because it's possible, easy and standard, and has been for 20+ years.