Probably it's this reason.
I knew people, from different countries who experienced similar, some were demotivated for joining, but others just payed, the fee is small.
I think it's ok, if you consider your participation in forum seriously - why not to pay.
And if you take part in bounties, 1 or 2 bounties can pay more than this small fee
Dude, did you read other posts in this thread? OP and his friends were banned for plagiarism, it's not problem with evil IP or something similiar.