As stated earlier, mostly for run times, and to prevent premature cuttoffs. One thing to note, some modern brushless systems have a high amp draw at full throttle. Even good Lipos can/ will have a voltage sag in those conditions. Often times, you can hit LVC of 3.4v, and by the time you pull the battery and check it, it's rested long enough to go back to 3.7 or higher depending on the pack.