If you and your friends take some cRPG gold to buy silver and Strategus troops, you can host your own Strategus battle with a minimum of 12000 exp every 2 minutes, and the more well-equipped enemies die, the more extra exp you get additionally to the base rate of 12000/2min.
Creating an easier way to convert cRPG gold into experience would add incentives for leeching, scamming others on the market and using shabby gear in general. The game would be even less beginner-friendly because rich people would not even have to work hard for their experience, because their gold can buy everything. Also, developers cannot add any number of servers if the donations stay at their current level, because someone has to pay the servers. I think it is good the way it is atm.