Why are people fascinated by my balls?

I have a pair of those Chinese stress balls sitting on my desk. I've had them for years but just found them the other day and put them beside my wire-frame office depot pen holder just to the left of my desk clock that hasn't had batteries in it for over 3 years and underneath my "Nukes, because sometimes you're tired of talking" poster. Since the moment I put them on my desk everyone that has entered my cube has commented on, or played with my balls. I'm not complaining, but it's just odd that something as unimpressive as 2 ball bearings with little bells inside would have such universal appeal.