Here's a list of possible reasons why people went through the inconvenience:
(1) His innate charisma
(2) His bulging wallet
(3) Have a secret crush on Steve Ballmer
(4) Hoping Vista will crash during demo
(5) Nothing else to do in Vegas on a Sunday
(6) Forced to attend by hyper-cruel editor
(7) Committed masochist
But let's be realistic. Obviously, (1), (3) and (5) are patently false, and there are better options for masochists in Vegas (Celine Dion or Liberace, for instance). So we'll play the evens and plump for (2), (4) and (6).
It certainly isn't a case of coming for the content. All the big announcements (Vista, pairing with Ford, Live gaming for Windows) have been foreshadowed well before time and endlessly covered online. The central theme -- Connected Experiences -- is no different to what Microsoft's been saying for a decade or so. Gates' final demonstration of how the "connected home" might work also bore more than a passing resemblance to scenarios discussed in his infamous 1995 book, The Road Ahead.
Two new products got mentioned in passing -- Windows Home Server and IPTV for the Xbox -- but the former was largely promoted via a commercial and the latter only ran onscreen for a few seconds. And unlike last year's celebrity-packed event, Gates was easily the most famous person on stage.
When I first saw Gates give a public speech, in the Sydney Opera House back in 1994, the company wasn't afraid to demonstrate products (an in-beta Office 95 in that instance), even if there was a high risk of them crashing. Microsoft seems to have grown more cautious since then, however.
Most of the Vista features demonstrated -- ShadowCopy, photo editing, the Office ribbon -- have been seen many times before, and posed no real danger of bringing down any systems in place. Even so, showing videos was a much more common tactic than running software.
The riskiest demonstration was a new Vista Ultimate Extra, DreamScene, which lets you replace a static desktop with a moving video image. Surprisingly, this worked, though I can only imagine it's a complete resource hog. Doesn't Microsoft remember the waves of public apathy when it introduced Active Desktop? At least this one's optional.