actually, i have a few reasons.
1) it gives me something to do.
2) it lets me try out new programming techniques in a low risk, low security environment. php OOP implementation is sexy, and im making sure its stable for a bigger project (my newest game idea)
3) it puts all the information regarding item trades and sales in one place. do you like going through the forums looking for ads and then oocing on the game waiting for people to come in contact with you? i dont. this, i think, makes it easier to locate goods and services.
the biggest reason im asking for input on this is the fact that i dont want to spend my time programming if it isnt going to be used. i rather it be used by 2-3 people than 0. and anyways, its deciently difficult debugging your own code if you dont have other people to help you break it.