“I don’t know the reason for sure.”
Ummm... maybe to sell more batteries?
Just ribbin ya!
Anyways, no matter what, one thing I should emphasize I DO NOT recommend that anyone use an auto-type charger for this types of operation. The reason being that an auto charge has a much higher amperage output than any type of trickle charger.
REPEAT: DO NOT USE AN AUTO BATTERY CHARGER!
Ok, so I have the auto-battery charger hooked up and charging. Now what?