Taps for a white, black, or green
The three colour decks are a little more vulnerable to mana base disruption and the mana bases are harder to optimise so can turn out very clunky in a small draft where you see less cards
rather, it's a combo of Wizards taking the aftermath cards as an opportunity to clean up a confusing rule and also to protect Standard from weird interactions between aftermath and things like Goblin Dark-Dwellers and As Foretold
Goldmeadow Harrier didn't exist yet but would be printed in Lorwyn later in the year
Lots of printings of this already, so youre dealing with people whod want to upgrade what they have from Mirrodin Besieged foil or Masters 25 foil
They also have dedicated land support with Haven of the Spirit Dragon, Crucible of the Spirit Dragon, and Temple of the Dragon Queen, making it easy to support a 5-color dragon deck