I take lots of pictures of my hands. Sometimes, I am holding stuff too. :)
I tend to use my hands for scale in my pictures. These destroy the artistic side of most of my photographs, but I include them anyways... Let me tell you why!
First of all, I use my hands to focus! My camera is a point-and-shoot, and so many times, especially when I am trying to take a picture of a small flower, my camera intentionally avoids focus on what I want it to focus on... It can be quite frustrating... So, my hands give it a bigger target. This is my reason of "practicality."
I like to include a little bit of a scale with my pictures too -- I very rarely go out into the field without my hands. ;) Sure, they aren't as exact as a ruler, but anyone could tell an inch from a foot when you see my hands. If you are curious, here are my measurements: from the top of my wrist (bottom of my palm) to the top of my middle finger, it is 19.5 cm. My pointer finger is 79 mm, my pointer finger nail is 12 mm, and the width of my pointer finger is 17 mm. :)
Anyways, this is why I include my hands in lots of my pictures. Scale and focus! :)