3 reasons:
1) all CREATIVES in Hollywood are mostly on Mac, even when running Avid. I imagine it's more of an homage paid to the computer they use to write scripts / edit sound/video / email / work budgets & calendars / etc.
2) Because of this, they're readily available over PC's in the industry of creatives. Plus, if u were writer or propmaster, wouldn't u throw in your mac just to say "yeah, my mac's more famous than me. It was in a movie" 😀 Maybe get an extra buck on craigslist a couple years later.
3) Apple is a brand that can speak levels and layers about a character. Sex n' City / Legally Blonde = 'here's someone that... wait for it... thinks different' 😉