I remember traveling through India, being amused at cars turning their lights off at intersections to save on electricity & bulbs. Where I live (not India) Motorcycles and Rental Cars have their lights "hot wired on" all the time. Everytime one of my home light-bulbs "blow" it's when I flick them on, maybe I should leave them going all the time!......whats my point!!..... it depends on your economics what you do.
My Company SOP is for Position lights to be on as an indication the a/c is powered, they remain on regardless, amongst the other things already described, it makes it particuarly easy to pick up a failed bulb on a walk-around, and extremely useful in contrasting and determining relative bearing and direction of other a/c, day and nite. especially on the rwy.
The Atmosphere I Operate in has a constantly changing viz from minute to minute, there is no way I am turning the Position lights on/off as I go into and out-of IMC or other areas of poor viz, "Set it and forget it" overall its gotta be safer.
PS; WHATUNION, Do you mean Cabin lights? have never heard of position lights powered from a "Hot bus" (standing-by to be corrected) therefore the problem is the Bat being left on, not the position lights which by that stage are your only chance to notice the a/c is still powered!