Because Moto decided to fill some of the home pages with reasonably relevant widgets and apps. Just that they're "out of order" IMHO.
I could delete everything off one page only to add everything from another page to it, and then delete all that off the original page, and move stuff from another page, etc, etc. But wouldn't it be just a lot easier to somehow say, "Move page 3L to 1L" (by dragging it or other settings)?
(Yes, it would be valid to call me "lazy", but as you both mention, the pages are supposed to be completely customizable, it only makes sense that the order of the pages could be easily re-arranged too.)