why are electric field lines always perpendicular to the body of the conductor?

this is correct only in static condition , and otherwise charges moves in electrical field projection over the surfaces , in case of a conducter conducting electricity , there is a drop in voltage along the conducter , thus some electrical field projection in that direction . 

so, it must have to be perpendicular beacuse it cannot be parallel and sometimes it have to be tangential . 
HOPE IT CLEARS ..