Arduinos are for prototyping, which makes the application fairly massive. The company I work for used them to develop one of our machines before we moved to a custom board. So, I'd say they are pretty useful.

Agreed, they certainly can be/are useful (and fun!), in a multitude of ways, but all too often I've also encountered peoples' "complaints" that they bought a bunch and now don't have a use case for it/are searching for one :)

That's because a toy engineering project is still an engineering project and will be way more work than you think it is, no matter how much work you think it is. It's hard to maintain that energy for long when it's not your day job (sometimes even when it is, tbh).

LOL. I often tell people online that they're better off downloading the free Arduino IDE or playing around with the Wokwi simulator until they have a good idea of what they want to build and whether or not it's within their capabilities before buying parts.

I've built a lot of custom arduino-based projects for other people and a substantial fraction of them are the "I bought a bunch of stuff, but I don't have time to learn how to program it" types.

Come on! They are for tinkerers!!! Same as such a robot.

You can use an Arduino for virtually anything though. A robot arm can only move stuff around.

Arduinos are also $20.

Arduinos are like $3 if you buy Chinese replicas with the old bootloader ;)

$20 will get you a 32-bit processor (ESP32), with Wi-Fi and Bluetooth 5.0 built in and a 2.8" color TFT screen, programmable with the Arduino IDE.

$3 will get you a basic Arduino Nano clone.