Yeah, it might not be 100% true for them all. I guess there are a couple that embrace the opensource scene. But the majority want to make all their stuff proprietary, and then rely on copying everyone else when new payloads and such are created.
They should just really tell you what chip it has, what size flash, and use the already existing tools out there to program them. This way the end user wouldn't be dependent on them for software. The only thing these companies are making money on is selling the hardware.. so just sell it, and leave it open.
Doesn't really matter to me much though. I already have my 3 different usb dev boards (tensy 2.0, AT90USBKEY, and sparkfun avr stick)... all of which are open for the end user to do whatever they want with them.