Should I run Defraggler on devices?

I run Piriform’s Defraggler on my 2 pcs. One of the pcs is used mostly by my young kids. So when I run Defraggler, should I have it also do the devices that my kids have left plugged in? I was just wondering if it could hurt the devices or would it even help them.
Also, I see my MAXTOR USB backup hard drive in Defragger on my tablet and I’ve been wondering the same thing about it.