The song Agua, by Jarabe De Palo, begins with:
¿Cómo quieres ser mi amiga?
The YouTube video of the song says that this translates to:
How come you want to be my friend?
"How come" is synonymous with "Why".
This lyric is the first time I've encountered "cómo" used to express "why".
So for you native Spanish speakers out there, is the following true:
¿Cómo quieres ser ...? = ¿Por qué quieres ser ...?
If yes, is the use of 'cómo' to express "why" something that is frequent in the world of Spanish?