Teiresias - why change back?

You know the story of Teiresias? Oh sorry, I keep forgetting that a lot of people don't know the old Greek myths. Teiresias was a blind seer and prophet well known in Greek mythology. There are two stories of how he got to be that, the transgender version and the non-transgender version. The transgender version is much the more interesting.

As a young man Teiresias came upon two snakes which were, as they say, 'coupling'. He struck them with a stick to separate them, and was magically transformed into a woman. Teiresias lived a full life as a woman, even marrying and having children, but many years later (the stories usually say seven years) again came upon two snakes indulging their carnal appetites. She again separated them with a stick, and was magically transformed back into a man.

Zeus, the ruler of the gods, and his wife Hera were having a dispute about who got the more enjoyment out of sex, men or women. Naturally Zeus said women, while Hera maintained it was men. Since Teiresias was the only person who had been both a man and a woman, it seemed logical to ask him to resolve the dispute. He sided with Zeus. Women, he said, get nine times as much pleasure out of having sex as men. Hera in a rage struck him blind, but Zeus by way of compensation gave him the gift of prophecy, as well as a greatly extended life span.

As a blind seer Teiresias appears in many Greek tales, including the Odyssey and Sophocles' Theban plays (about the story of Oedipus). As a prophet he was supposed to be infallible.

There is an interesting parallel here with the Native American idea of 'Two-Souled' (Intersexed or Transgendered) people having a sacred power.

But linked to the interesting recent discussion 'The unwritten TG story rule, never change back the transformed - why?' started bv clancy688, I ask: Why did Teiresias strike the snakes on the second occasion? Why did she change back?