I don't think that's the reason why. Track pads are just another part of Apple's obsession with UX. They invest millions (literally) into track pad placement, feel, and ability knowing that users care about it and they'll make it up with volume. It's hard to justify UX spend.
Yes, these comments are exactly right. The other companies resigned to it being Good Enough for them, and don't care about making the trackpad excellent.
I'm not positive but I would guess that the hardware is pretty similar. The same manufacturer, synaptics, made the touchpad in my MBP and Thinkpad. Yet the Apple touchpad is far superior. Aside from the fact that my lenovo has a textured tract pad, I think the Apple software is just that much better.
Apple acquired FingerWorks[1] in 2005. They were pioneers in multi-touch pads. I believe their technology is one of the reasons the original iPhone was successful.