How essential is shielding?

Both my analog interconnects and my speaker cables are unshielded, yet my system is pretty much dead quiet. This is making me wonder whether the importance of shielding is sometimes exaggerated.

The majority of cable manufacturers seem to emphasize shielding as an essential feature of design. I don't doubt that there are many situations where shielding is both necessary and effective. But my results with unshielded cables makes me suspect that there are also situations where shielding is unnecessary or even detrimental, and that these situations may be more common than would be suggested by the dominance of shielded designs.

How essential do you think shielding is?

Thanks for any input,
Bryon