>Also (and mostly) because Microsoft will come down on them like a ton of bricks if they do. Since most of their business is selling Windows machines, losing that nice discount on Windows would be tough on them. Hardware vendors live by selling hardware, and if Microsoft didn't essentially pay them to push Windows they couldn't care less which OS went on their computers – they would happily sell you CP/M if it helped them move more boxes. Besides, the kickbacks from pre-installing junk software on top of Windows are nice if you're a hardware vendor.
Yes the big "institutional" vendors, Dell, HP etc... might be exactly like that, like an implicit blackmail threat, comply and have bonus or else...
But what about letting the "potential" Stormy Peters do it lol (just an example with a picked name, nothing relevant or personal) http://lwn.net/Articles/541625/ ... i mean there can be many "local" smaller vendors in a model similar to the traditional white box model, but attaching themselves and their clients to a model resembling Android, with free and non-free (per say), paying or freeware "appstore"...
The main distros are only a repository / appstore, the local and other customizations is up to those small vendors that can derive a good business out of the hardware selling (and customization that could surpass windoze by miles, or any attempt to emulate by any distro-> simply because one size can't fit all).