thats because their registry is archaic. you have to register a domain by emailing a specially formatted text file to the registry. its quite complicated and if anything is off it bounces back and does not complete the registration. Plus you have to have your nameservers set up in advance, or it also will not let you register. You can buy through resellers but they are mostly reseller hosting companies that want to lock you in to their services by not letting you set your own nameservers, or otherwise their prices are 6x to 20x the registry pricing.