"...However, I can't help but think that most people who have purchased an iPad were content that it had no keyboard, and those who were not and didn't buy one bought a netbook instead."
Because most netbooks are crappy little mini-notebooks with dinky little keyboards and crappy low-res screens. They don't have the battery life or form factor of a tablet.
Most of the time, a keyboard is not really needed. But can be handy for someone who has an iPad who ends up wanting one, rather than getting rid of the tablet to get a netbook.
Apple doesn't make netbooks. Their smallest / bottom end notebook is the Mac Air.