It's because people don't like his character. From the very beginning of the campaign the overwhelming response has been "I like the PC guy but the Mac guy comes across as a smarmy little smart-arse" and comments of that ilk.
I'm not a fan of the campaign in general, it still over-emphasises the creative side of the Mac rather than showing just how capable the platform is (only one ad dealing with the more work-focussed aspects? Not good enough.) and once again shows the Mac to be the quirky young upstart to the PCs more mature, buttoned-down persona.
They need to show the Mac and the PC competing in the same thing, put both online with the settings they have out of the box and show what happens after browsing the net with their default browsers for a while. Actually SHOW how much easier it is to make a home movie, SHOW them both running Office, just bloody SHOW THE OPERATING SYSTEM!!!
I know that would involve directly competing with Microsoft but geeze, at some stage Apple are just going to have to bite the bullet and show to the public how things work on a Mac.