I believe open source silicon design has much more to offer than just lowering unit costs and increasing profit margins for the existing dominant players. This is why we are established as an independent not-for-profit - we want open source hardware to benefit everyone, and its design to be a truly collaborative process. We have a long way to go, but that's the direction we want to help move things in.
We are set up as a UK Community Interest Company, which that means we define a particular community we hope to benefit. For us that is anybody who may either adopt or benefit from open source hardware - whether they're a hobbyist, academic, small startup, established company, and whether they're currently sponsoring our efforts or not.
For a more recent interesting example, Josef Prusa built and gave away its design for its 3D printers, they were cloned by dozens and sold everywhere in the world. When he launched his company, he had instant recognition and thousands of customers ready to buy. (The reprap community is a fascinating example of real open innovation, advancing very differently than labs or startups or big companies would)
And arduino uses UART bootloader, which uses up UART port and doesn't offer debugging. They have addational chip on board for usb<>uart, so why not instead use uC which can act as programmer and debugger using normal interface?
Atmel(Microchip now?) also have some nice XMEGA uCs with much more perpipherals that ATmega series, but are pretty expensive.
As a standard, users benefit from being able to share instructions that have a high chance of working on someone else's system.
Obviously these are most relevant for beginners or those with a short time to invest. But that's the market that Arduino practically created. It simplifies the decision making process: if you're a beginner, start with Arduino. Once you've used it for a bit, you'll be aware of the limitations and have an opinion on which alternative to switch to.
There's literally no other systems that are as simple as Arduino for newbies to use. The only one I know that is vaguely close is mBed, but that uses an online compiler (gross), or a relatively complex and not that great CLI interface. Arduino's IDE may be shit but at least it is simple and easy to install.
Almost everything else involves complex JTAG/SWD programmers and weird OpenOCD command lines and frankly that is just shit. Even as an experienced embedded developer the state of the tools is embarrassing.
I'd suggest that the BASIC Stamp got there before the Wiring/Arduino: