Understanding "why else would"

Question

I have a question about this highlighted part of an ESL pod transcript:

Mandy: Whoo! Whoo!  Theo: Hey, get down from there. You shouldn’t be sticking your head out of the sunroof.  Mandy: I just wanted to get some air. This stretch limo is amazing.  Theo: Well, I thought I’d rent one and take you to the prom in style.
Mandy: This is the height of luxury. You’ve really outdone yourself.  Theo: Thanks, but maybe we should be careful not to spill drinks on the seats.   Mandy: Everybody drinks and parties in the back of a limo. Why else would they have a wet bar?  Theo: Well, we shouldn’t be drinking out of it. We could get into trouble.  Mandy: The chauffeur doesn’t know what we’re doing back here.

Does ** why + else + would has a grammar usage? And what does this question mean? As it is very difficult to understand could you please provide me with some more examples?

Answer 1

"Why else" is a common construction in conversational English, meaning, "for what other reason". Read that sentence as "For what other reason would they have a wet bar?" This is a rhetorical question, i.e. a question that has only one possible answer, used to prove a point. There is a wet bar in the limo, so if it's not to provide drinks, what other purpose could it have? One could say this is rhetorical use of Occam's razor; Mandy uses it in a cutting manner.