First off, if you don't understand Twi'lek, most speak either Aurebesh or Huttese (the second most wide-spread language besides Aurabesh).
And Spooky's right. Twi'lek society finds its females stuck in our version of the '50's with a Gorean twist. It is thier duty to please thier men on Ryloth, and that habit has carried over into the rest of the galaxy. Not every single Twi-lek female is subservient, but most are, due to millenia of social structure.
On a side note, a female Twi'lek Jedi is highly sought after for her ability to infiltrate. The concept of subservient females is so strong throughout the galaxy that most beings instantly discard thier prescence as no threat.
Nice pic, I love it!