Why was the automated system not programmed to adequately inform the pilots of their exact situation, ie:, no reliable airspeed indication resulting in AP disconnect?
The automated system is not capable of reasoning. (Otherwise we would be talking about Artificial Intelligence.)
It is easy for you to make the connection between the two facts. Not so for the system. Producing a relevant, non-cryptic error message for the end user, may very well require a complicated algorithm of its own! Think of error messages that you get from your computer sometimes, how helpful are they to immediately understand the root cause of the problem??