There seems to be a widespread view that lead shielding around a person or object will shield it/them from scrying. 

I am having trouble locating anything in the rules that states this is the case. Is this just a commonly used house rule that I've missed somewhere, or something? Wouldn't this cheapen or completely invalidate the need/utility of *nondetection*?

There are a number of divination spells that can be foiled by lead, but scrying isn’t one of them.

You also can’t scry on an object, only a creature or location.