Because prop departments are huuuge huuuge ventures on their own hiring hundreds (if not thousands) of people. They usually create few version of the similar prop (in mentioned scene it wasn't the same as one should be faxed and second handwritten).
Because those two scenes were filmed in different location, in different time. Keeping hold on every prop (and even stapler on third desk from left is prop) would take hundreds of workhours. And would require filming according to event in movie you see as the final cut. While in reality one scene could be filmed at the beginning and the second ad the end of filming. The scenes in script could be added later, there could be few scenes in between and so on.
And the props work in a way that they, if the props are not valuable enough to deserve their own people, split scrip by pages and give it to different people.
There is a polish movie "Nic Śmiesznego" where they put a scene of a guy researching "forest" as filming location 100 km away from filming base.
Director: Why the F*K would I need a forest
2nd Director: it's in the script
D: Where in the script?
2nd: "when they rode above the hill they've seen a forest"
director take the script, turn the page,
Director: turn the page and read it
2nd: Oh f**K
D: read it
2nd: when they rode above the hill they've seen a forest.. of crosses
So for you that scenes are next to each other and passing the note to next scene should be easy when in "behind the scenes reality" those two could be miles, weeks and props managers away from each other.