Come to think of it, why do we tie a string around our finger to help us remember things? There's probably no scientific basis for that belief, but we believe it anyway.
EDIT: And because things like this bug me unless answered, I researched a bit and this was the only thing I could find attempting to explain it.
I am easily distracted and I tend to forget things easily, so I thought to post an online note to remind me of the things I need done ASAP.
Oh look, a squirrel!
I mean, here's my to-do list for this week.