Just for giggles, I went clicking through the list of top-level national internet domains on Wikipedia. Quite a few of them are for territories that are not independent nations. Why?
It doesn’t seem that geographical distance is necessarily a determining factor - Puerto Rico and the US Virgin Islands are much closer to the mainland USA than Alaska or Hawaii are, but they have their own domains and Alaska and Hawaii use .us.
Is it a lack of participation in the “parent” government? That doesn’t really describe the French overseas departments, which have their own domains, yet as far as I can tell, are as much a part of France (politically) as Paris is.
And what the heck possesses anyone to reserve a domain for uninhabited places like Bouvet Island?
You might as well ask why Puerto Rico has its own Olympic team, and why Scotland plays in the World Cup.
The answer is: because the people who organize these things said they could. As it is with country-code top-level domains.
The ccTLDs are administered by the Internet Assigned Numbers Authority, and they have assigned a domain name for almost every country and territory listed in the ISO-3166 standard list of country codes. Where possible, they delegate control of the ccTLD to some national or territorial political entity in that nation or territory. As for Bouvet Island, apparently it’s in the standard list but control of the domain remains undelegated.
Here is the Wikipedia article on ccTLDs. They list six interesting examples of ccTLDs which do not appear in the current country code standard. Some interesting examples:
.uk - the country code is actually GB
.su - former Soviet Union; there’s now .ru for Russia and codes for the other former Soviet republics, but .su remains entrenched.
.yu - former Yugoslavia, to be phased out in favor of .rs (Serbia) and .me (Montenegro)