One big difference between the Megillah and every other part of Tanach is that the Megillah was mass produced by non-Jewish scribes.
For the first time there was a risk that many copies would be thrown away or abused. Hashem’s name doesn’t appear in the Megillah for the same reason that we write G-d. An indirect reference to Hashem ran into a related problem. The scribes doing much of the writing were idolaters. A reference to a Creator would have been written with a different intention in mind. A Sofer takes great care before writing the name of Hashem to purify his intentions.
There was no possibility of pure intentions when writing the Megillah. To avoid a desecration of Hashem’s name in a document that is meant to serve as a consecration of Hashem’s name, the name was left out entirely.
The omission of Hashem’s name was an adaptation to a very modern problem that we deal with all the time.
Samurai Mohel 