Because a lot of people here use a MBP as their main development device, at least from what I've seen in the comments.
However, this topic being near the top of the front page does amuse me, because I saw several accusations of HN having a strict anti-Apple bias. That's not to say that there's a strict pro-Apple bias, however, just that the community seems to be genuinely split.
I mean, I am very opposed to everything iOS because of politics, but I am very pleased with my MBP. I don't need to downvote Apple's announcement of new MBPs just because I don't agree with the politics surrounding iOS.
Yeah, I was a little vague there. I didn't mean to imply that people interested in MBP would be supporting everything done in iOS, just that there was not a simple pro- or anti- Apple opinion here. Thank you for explaining that better than I did.