Multiple factors here:
First, Iran does not want to escalate into openly armed conflict with either the U.S nor Israel. They want to poke the bear enough and save face enough without having to expend significant resources and lives in such a conflict. They are cowards but smart cowards.
Second, yes the Iron Dome is pretty darn good. They are constantly upgrading it and we are helping them with it.
Third, we have multiple Fighter Squadrons deployed here with their radars pointed towards Iran after alerted. They’ve done a fantastic job eliminating most threats flying from the East. They’ve been supported by an increased Joint Early Warning presence between Cruiser Destroyers, E-2s, etc. Iran is also learning how to circumvent this increased presence.