Hamas understood that they could fire without any response from the IDF
During Operation Cast Lead I was a part of a target designation team. Meaning, a team that is located within Israel and is watching inside the Gaza Strip and directing attacks towards enemy targets. Whether it is artillery or a helicopter attack, the directions must be very specific and precise. If there is a rocket launch from inside the Strip into Israel, we must see exactly where it was fired from and verify what is in the vicinity and whether the place is clean. Meaning, that there are no uninvolved civilians in the area or an ambulance passing by. Only then there is a permission to launch a counter attack.
During the operation, there was a humanitarian ceasefire every day between 13:00 and 15:00. What it meant was that regardless to the status of the troops on the ground or the security situation the IDF decided unilaterally not to attack. What happened on a regular basis was that every day during those hours there were massive rocket attacks towards Israel because Hamas understood that they could fire without any response from the IDF. In any such event we had several options: to attack from the air, to send infantry troops or to do nothing and respect the ceasefire. I remember there was a discussion about it, but eventually it was very clear what we should do. Once we decided it was clear, we refrained from retaliation.