Not trying to troll - just don't know. Why would anybody use an Arduino versus a five dollar Raspberry Pi Zero?
1.) Pin control simplicity - Arduino's bread & butter is basic logic statements wrapped around pin signals (e.g. if pin #1 receives an inbound burst of electricity, tell pin #2 to send an outbound burst of electricity). Since most commercial processes are loops of very specific routines, this is all that's needed (not to mention it's easily scalable to massive operations).
2.) Battery backup - Raspberry Pi wasn't really designed to be powered by batteries, and voltage fluctuations lead to crashes. Also, since Raspberry Pi requires more power (than Arduino) to operate, it would eat battery life much faster.
3.) Startup consistency - When Arduino is powered on, it has a consistent startup that quickly loads your sketch. The restart behavior is predictable and downtime is minimal. With Raspberry Pi, you're dealing with an operating system starting up. This makes it much more cumbersome to get back to where it was prior to loss of power.