I guess I rarely see the case for an AVR when you're not prototyping on an Arduino. You can get chips that are an order of magnitude more powerful per $/watt/and any other metric you'd want to use.
Have you read "The Amazing $1 Microcontroller" [0], which might have been posted here before? It's a survey of available microcontrollers, with the intent of helping you choose one. If you have read it, are you in agreement with the article, for example on how AVRs compare to others?
I haven't confirmed what you've said yet, but it makes sense since 8051/8052 MCUs are generally used for their compatibility with legacy code.
I've been working on an agricultural spray controller that uses some silab part only because there is already assembly code written for it. The company that sells the controller doesn't want to spend the time rewriting it in C and moving to arm or pic.