FireWire's there because that's what the iPod 3G-5G, plus iPod mini used as 'primary'.
The original iPhone, along with the iPod nanos up to 3G, can charge over FireWire (even when not jailbroken,) but don't contain any data-transfer logic for FireWire. The iPhone 3G and iPod nano 4G+ can't even charge over FW. (Had to get a new car charger when I got my 3G.)
They may be able to re-use the FW data pins, but the power pins are off-limits. You don't want to have someone accidentally plug in a new device that expects those 12V pins to be anything other than 12V, into an old device that spits 12V out over them. (Like my speaker dock.) I'm just annoyed that newer speaker docks don't give out 12V "FireWire" power. My old 3G iPod works fine, other than a dead battery, and I'd like to get a new speaker dock; but none provide 12V power for it.
(The 3G iPod, the first one with the dock, will sync over USB, but not charge. It requires 12V FireWire power to charge. All newer iPods can USB charge.)
The original iPhone, along with the iPod nanos up to 3G, can charge over FireWire (even when not jailbroken,) but don't contain any data-transfer logic for FireWire. The iPhone 3G and iPod nano 4G+ can't even charge over FW. (Had to get a new car charger when I got my 3G.)
They may be able to re-use the FW data pins, but the power pins are off-limits. You don't want to have someone accidentally plug in a new device that expects those 12V pins to be anything other than 12V, into an old device that spits 12V out over them. (Like my speaker dock.) I'm just annoyed that newer speaker docks don't give out 12V "FireWire" power. My old 3G iPod works fine, other than a dead battery, and I'd like to get a new speaker dock; but none provide 12V power for it.
(The 3G iPod, the first one with the dock, will sync over USB, but not charge. It requires 12V FireWire power to charge. All newer iPods can USB charge.)