The IDF spokesman’s blog asks the question, whey are the number of Israeli casualties so low – and answers here. The short version, we have the Iron Dome System that destroys some of the rockets before they fall, and the people have access to bomb shelters – either in their homes (the safe room, or mamad in Israeli slang) or in public shelters in their apartment buildings.
The long version of this answer is our society and its values. We Jews value life above (practically) all else. We use our human and physical resources in order to do whatever we can to save lives. We use our superior technologies to help us survive. Unfortunately we have had a lot of experience in warfare and defending the homefront, and we try to learn from every war. The fact that we have safe rooms in houses came about as a reaction to the Gulf War in 1991. After that war a law was passed that every new residence was required to have a safe room built into it. These safe rooms have literally saved thousands of lives, just in the past week.
The IDF youtube site has a short video showing the incredible damage to an apartment in Rishon LeZion hit yesterday, and at the end it shows how the safe room is completely intact.