Charging Battery with Alternator - Warning

Maybe i am missing something here, but what is the purpose of a voltage regulator, i thought once the battery was at full charge, and by driving 5 to 10 minutes the regulator steps down how fast the charge is according to the number of things like lights and wipers, if your alternator continued to charge at the same rate any time you started your car, if the regulator don't drop the voltage to the battery, it wouldn't matter if you had a weak battery or not,your battery would explode