It's not illegal.
I agree it's not fair. Sometimes life isn't fair.
I work for a company in the UK that's involved in marketing, including on-line. Our customers (i.e. businesses) pay us to deliver advertising to their customers, who are all in the UK. Why should those companies pay to advertise to people who can't buy their products? Similarly, Top11's advertisers are only going to pay to advertise in countries they're selling in.