Because for the average user, the features and power of a "Good" IDE are at best a nuisance and at worst a barrier to entry. I've tried using some, such as a b

Because for the average user, the features and power of a "Good" IDE are at best a nuisance and at worst a barrier to entry. I've tried using some, such as a brief stint with Atmel Studio some years ago, Eclipse, and a couple others I can hardly remember. My biggest complaint was how tedious it was to start a project. They start asking you questions that a hobbyist isn't going to have enough background to answer. Arduino takes those and hides them. Yeah, it means you might have less flexibility, but by the time those important hardware details actually become relevant, the user has probably amassed enough experience and knowledge on micros and AVR chips that they'll now be able to use those fancy IDEs. Arduino isn't about being the final product, or for becoming the next best IDE, it's about teaching, learning, and prototyping. It's about teaching a generation that programming, hacking, and technology isn't out of their reach or understanding. I've taught middle schoolers from rural areas in Puerto Rico how to control things with an Arduino. One of them build a timer/thermostat for their house using scavanged IR leds from a broken TV remote, a few passives, and a temperature sensor that costs about $0.50USD. He now has a system that will turn on and adjust the Mini-split AC unit in his room, so it cools his room down slightly before he gets home. His unit was an older, cheaper model that did not have a built in thermostat (or the thermo died, I'm not completely sure). That student now wants to go into Electrical Engineering in college, and now thinks he stands a chance at getting into college, where he didn't before. That is why Arduino is so popular.