I started doing such things after finding some entertaining notes in hard to find/reach places. I found that it had added a lot to my experience and I would like to do the same for others.
I found a chick cubimal a few weeks ago too. Very cool, and thanks for to the Glitch that did that! I will likewise think of something fun to do with my duplicate cubimals :)
Back in beta I found something hidden in a tricky spot with a note to feel free to take and leave something else. It really added another cool dimension to the game for me, so I leave stuff in tricky places, too, though i'm too lazy to add notes. Thank you, whoever you are who got me started!
When you find a free item it always makes your day, no matter how little it is. I like to drop things I know im not going to use so I can make other peoples day.
p.s: What are cudimals?