[HeyLaughingBoy]

having a standard test bed for devices is such a massive annoying failure in electronics

This is a very well phrased description of a problem I've seen for a long time. I'm not an Arduino user: I prefer to use "raw" AVR devices in my own circuits. But something like the Arduino, like the BASIC Stamp before it, provides a sort of "language" to explain how to do things that was missing before.

In the days of PC's with printer ports, someone asking how to blink an LED under computer control could be given a simple answer that would have them up and running quickly. Now we need to find out if it has a printer port, or maybe a serial port to use one of the control lines, or otherwise suggest purchasing a USB device to use instead...

But with something like the Arduino available, the answer can be as simple as "buy this device (Arduino) from this vendor and run this code and your LED will blink." From the very beginning, the people involved are using a common vocabulary: the same development platform. And that has benefits that cannot be ignored.