"People who are really serious about software should make their own hardware."
- Alan Kay
http://www.brainyquote.com/quotes/quotes/a/alankay375550.htm...
I agree that both manufacturers and carriers are incompetent at software -- that's probably why my phones run so much better and faster with a custom ROM put together by some hacker in his basement. In my opinion, if the software wasn't tied to the hardware the result would be better.
http://androinica.com/2010/07/14/motorola-says-if-you-want-t...
http://www.tomsguide.com/us/G2-HTC-G2-Rootkit-Jailbreak-G1,n...
Android isn't really tied to hardware very much unless the carriers make it so. Hell, I can run Android on my Windows Mobile phone (Samsung Omnia II.)
AFAIK, the real reason is that there is no standardized design for phones, whereas most desktop/laptop/servers look basically the same to the OS.
But why must the software be explicitly tied to the hardware? We don't buy desktops or laptops that way. I periodically upgrade the ROM in my smartphone and the result is amazing. Why should I have to toss a perfectly good piece of hardware just to get software improvements?