[wildzzz]

Why use a $20 Arduino when you could have just gotten a $1 custom PCB, $0.50 microcontroller, and a handful of jellybean parts to do the same job? Because one costs less in Non-Recurring Engineering (NRE) than the other, you'd have to design the schematic and layout and then select parts that are affordable and available. Sometimes its just makes more sense to use a reusable component than doing something custom, especially when you don't plan to sell a lot of them. Someone needed a 1-to-4 decoder and for some reason, couldn't find one on the market that fit the application. The Gate Array already existed and was cheap to configure so that's what they went with. It's overkill but so is getting a brand new die made for such a throwaway part of the design.