Leg Cramps

I've gotten leg cramps off and on for almost 6 years now, usually at the start of summer and winter.  I don't know why I get them so bad, but they hurt!  And they don't just hurt when I get them at 3am, the entire next day and for a few days after, my legs are very sore.  But, I started wondering, why are they always only in my feet, shins and calves?  Why never in my thigh, or my butt, you never hear anyone say, Oh I had some bad butt cramps last night, lol!  And why never in your arms or hands?!?!  Yes, this is what I was thinking at 3am while my left shin and foot were tightened by cramps and all I wanted to do was sleep!!!