Testament said:WHY?
I can't answer for Korgoth, but the reason to make gold = XP is that it propomotes exploration. It is no diferent than using "story awards" to try and promote a more narrative playstyle. if it exists as an option, it means that the designers are willing to admit that there are multiple ways to play D&D "righT" and they are all equally valid.
As to demi human class/level limits: I can do without level limits, but making it clear that in a particular game it is perfectly reasonable for dwarves not to be able to be wizards, for example, will go a long way toward reminding people that "options" does not mean "evrything must be in every campaign". If they would have done this with 3E -- for example, lettinga legacy setting like FR keep class-race restrictions to maintain the setting's integrity from previous editions -- as the options bloat occurred it would have been easier for some DMs (me!) to restrict new options.