You also may be giving too much credit to Hamas and Islamic Jihad's ability to aim rockets at the intended targets. Plenty of the time they hit the middle of nowhere, or they've actually even hit Palestinian-dominated areas (Hebron and Bethlehem) [1][2]

In many situations, it makes far more sense to save the Iron Dome counter-missles.

[1]: http://www.maannews.net/eng/ViewDetails.aspx?ID=712463 [2]: http://www.ynetnews.com/articles/0,7340,L-4542242,00.html