This link may help explain the operation of.
http://www.forestriverforums.com/for...tml#post327988
Suburban does make a model with the electric switch inside. However, if you inadvertently EVER turn it on without water in the tank, then you get to replace your now burned up electric heating element.
Having the electric switch on the tank itself, let's you also verify there is water in the tank BEFORE turning on the electric element.
It's explained in the link.