[roland35]

That is a clever solution to a common problem with battery powered devices. Another benefit to the engineering side is that designing a custom battery is hard - you need to work closely with the battery vendor on the mechanical package and the electrical interface. The final battery may not have been available when the first prototypes were out! So having a AA option made it easy to test.

With the battery products I have been part of developing we had a wire lead from the battery which made the mechanical interface more modular. This was not a handheld device however, so the trade-offs are different. Blade or similar contacts are more user-friendly and reliable for many insert cycles.