I guess I could have just said that GB/GBC and GBA speak different languages to the hardware.
Its pulled from a different part of the hardware. GB and GBC games were programmed in Z80, the same as your TI-82 / 83 / 84 / 85 series calculators, and switched over to the Zilog processor when an older game was used. Gameboy Advance titles do not use this technology (it came out in 1976). Backwards compatibility rarely runs natively on newer machines. The same is true for PlayStation and XBox, in order to run older software, they need to switch to a different package whether it be a separate processor or through software emulation.
Yeah, I think we've all pretty much agreed that those nasty emails are coming from those pre-pubescent little buggers. I'm pretty sure that 13 year old kid isn't going to sue. If he had the money for a lawyer, I think he'd have enough to get a Gameboy Advance or fifty with some money left over for a car they can't drive. I wouldn't pay them much attention, they're going through an awkard stage in life. But if you see one in the street, hitting one is worth 10 points. (Note: Please do not commit vehicular homocide.)