We are in the process of adding some of the more popular new gTLDs introduced as competition for the traditional com/net/org/biz/info/name crowd. If there's a gTLD you're interested in that you don't see on our list, feel free to ask about it in our forum.
However, we are very hesitant to allow adding ccTLDs (the two-letter TLDs assigned to individual countries based on their ISO country code — all two-letter TLDs are ccTLDs) for countries other than the United States due to concerns about giving those countries political, economic, or legal leverage over us or our members. Most ccTLD operators are part of or run on behalf of the country's government, and they typically include something in their registrar agreement about "Paragraph 1219: You will follow all of our country's laws." and "Paragraph 2751: The ccTLD operator reserves the right to terminate this agreement at any time for any reason." Either could cause serious problems for us. Suppose, for example, that we offered registrations in Elbonia's .eb ccTLD and accumulated a few thousand .eb domains. Then suppose that the Elbonian government decided they didn't like a site we host that criticized their Grand Vizier's hat, and told us to get rid of it or have all those domains seized.
While that's a little farfetched, we have had conflicts with foreign governments over member sites, and handing significant leverage to people who may not have our members' best interests at heart doesn't seem like a good idea.
Many ccTLD's also have weird, special requirements and procedures that would require a lot of extra work for us to support. (Looking right at you, .uk, and your IPS tags!) That may not sound like a big deal, but "extra work" for us translates directly to "extra cost" for you. Some ccTLDs even have complex legal requirements that the registrar, the name servers, or the registrant be physically present in that country that would be difficult or impossible for us to meet, even if the technical issues didn't exist.