The Teiresias that I know is only in the play Oedipus, and there he (who used to be a she, and also a mother) was treated like this all-knowing wise man, very mature and intelligent, but later when I goggled him, I was so shocked with his story, what with the stalking Athena and hitting a couple of snake who were having sex (and got transform into a girly girl – is it just me or everyone can't see the connection of how being transformed into a girl can be a retribution from hitting snakes having sex?)
The myth of ancient Greeks have this reputation, full of sex, lust, fools, over-achieving man, out-of-your-mind punishment. I think Teiresias is all reputations rolled into one. One big reason for this is that he came out in a number of different plays so probably he needs to develop his characters more. Probably, the ‘tukang karut’ of ancient Greek have ran out of ideas so they decided ‘hey, why don’t we make him blind and after a few more stories, we could change him into a woman and he could bore sons!’.
Prophecy is not a good thing, i think teiresias, ironically, being a prophet himself, sees the worst in saying about prophecies, that was why he decided to keep quiet of saying who is the murdered of Laius.