Maybe a little of both for some women, but given the pain and cost of maintaining a nice Brazilian you can bet that the lady really, really likes how it looks and feels for herself, or really, really likes the effect it has on her man (or men, women, la crosse team).
In the long term, I don't know too many women who could maintain a Brazilian just purely for the pleasure of her sexual partners if she herself hated the process. On the other hand, I'm more than positive there are indeed women out there who go under the wax just to please others. If you derive pleasure from giving pleasure to others, then is there anything wrong with that though?
At any rate, my feeling is that the Brazilians has become one of many option these days. For a while, there was a lot of hype for the hairless look and every woman seemed mad keen on ripping follicles from their nether regions but I think the trend has died down a little. Many gals and guys enjoy a neat, manicured garden as much as a bald field. Some are even gravitating towards the au naturel look and bypass any depilatory action. Probably, most women will go from one look to another depending on various factors (and yes, including what gets their partners off).
I think you may end up with a few comments from the RHP ladies to further enlighten you and you might like to post it to Forums for what I am sure will attract some hairy debate.