There shouldn't be any reason as all possible reasons had been eliminated. Before the introduction of copper membership, project wanting to make an announcement on the forum, buy account to do so since newbie account weren't given the privilege of posting images but now things has changed as with just few dollars you can bypass most of the newbie restrictions and make your announcement.

I think the reason behind the unofficial banning of buying and selling of account on the forum is as a result of the level of farming that was ongoing on the forum before the introduction of the merit system. This farmers wee basically spamming and this was causing a nuisance on the forum.

Secondly any account that change hands wasn't to be trusted as a result of the risk involved, imagining someone buying a trusted account and the level of harm he can commit. You don't have any reason why you should buy an account, if you want to learn then start the learning process from the beginning.