It's that there is a pay-to-improve-stats culture.
Sure, a world first guild will smash any other guild anyway but between almost equal guilds:
1. One will have the funds to transfer realm and get the huge advantage they may consider with that change (e.g. a very small realm that gives them infinitely better queue times since they only cross-realm recruit anyway and they don't need the market).
2. One will have the funds to race change at will any patch forward and get a slight advantage on racials
3. Faction changes, boosts to save time from levelling (and get better stats earlier) etc.