Occam's Razor would be that the tens of thousands of marketers that Apple hires (contractors or otherwise) utilize the most obvious and effective strategy for making sales: Spamming the internet and manipulating perceptions. Their marketing personnel don't sit there thinking "well I'm only hired to market the low-margin Macs, so I guess I'll do nothing today."

Your argument is basically: Why would they try and make more money when they can just sit back and get rich off iPhone's.

That's certainly not a tenable position.