They're not (well, except some of them do try to cram on their additional 'useful' pieces of software on top of the OEM builds). But that's the game that they're then playing: the profit margins are much lower than what is currently achieved through selling mobile devices. There are a gazillion smaller manufacturers all competing for the same piece of pie.

I'm not sure many companies like HTC or Samsung or Motorola want to turn out to be the new Acers and Gateways (no disrespect to those companies as such).

It'll be very interesting to see anyway what Google does in 3.0.