Why would I want to download a 1800+ page manual into a smaller viewing space when I've already got a 23" that I can zoom in on and read while I have x1 chugging along?
They're great on trains, planes, in waiting rooms, etc., etc. It's not either/or. Anything you have on a Kindle can also be read full-sized on the PC with a Kindle PC app, plus they both remember where you were when you left off on the other, which is nice.
And yes, sometimes I do...

!
-Susan