Cost...and, it might be perceived that finding a circuit with double the power available wasn't as common in that market, which is what it would take to recharge the i3 at it's maximum rate with the KLE installed. It depends on your tolerance for unplanned trips, and the ability of the vehicle to recharge quicker to make that a possibility. With a KLE and max EVSE, 3-4 hours. Without a KLE, 6-8 hours to recharge. Either is easily attained overnight, but may not be if you do something late into the night and need to leave for work in the morning! Or, arrive home from work, and want to go out later.