Why is Antarctica governed by a treaty inside of a government? How might future developments in drilling and cold-weather technology affect the region politically?

There is no "Government of Antarctica" in the way that we understand it in the rest of the world. This is largely as there are no indigenous peoples and no-one lives there permanently, the only habitations are scientific stations that people visit for short time periods, usually from a couple of months to just over a year.

Representatives of the 12 nations met in Washington D.C. in 1959 to draft and sign the Antarctic Treaty - (summary here). This agreement dedicated the entire continent to peaceful scientific investigation. It came into effect in 1961 and all territorial claims were suspended. In 1991, 24 nations approved a protocol (addition) to the treaty that would ban oil and other mineral exploration for at least 50 years, this came into force in 1998 and stands until 2048, at which point it will be renegotiated, to change or remain as decided at the time. It is possible for the treaty to be changed before 2048, though it would take the unanimous agreement of all of the consultative parties to do so, as of 2015 there are 29 nations that are consultative parties.

There are now 52 countries that have signed the Antarctic Treaty - which represent about 80% of the world's population.

The key objectives of the Antarctic Treaty are:

To keep Antarctica demilitarized, to establish it as a nuclear-free zone, and to ensure that it is used for peaceful purposes only.

To promote international scientific cooperation in Antarctica.

To set aside disputes over territorial sovereignty.

The result is that Antarctica is one of the few places in the world which has never been affected by war, where the environment is fully protected and where the priority is scientific research. The Antarctic Treaty has ensured that this has continued and will continue for the foreseeable future.

The Treaty covers the areas south of 60°S latitude, extending to the South Pole.

In general for individuals at Antarctic bases, the national laws of their home country applies to them personally.