Somedood
Needs and circumstances differ. I am in urban/crime ridden area that is flat.
At constant velocity no change in acceleration so no force and no work. I know there are stop and starts. However, the extra weight for the lock is not as big a deal. Actually weight is not that big a factor on flat landscapes. I have fenders and racks and would not do without them.
I use a good U-lock and cable lock. I park in good, busy locations. I usually ride older bikes. Over the years I have had three or four bikes stolen. I expect a certain amount of loss to crime.
In the 70's when 10 speeds arrived on the scene, the best locks and chains were not enough. Some months ago I went by a bad area that happens to be at the start of the trolley line that goes down town. There is a rod iron fence going around a park. There on the fence was a shiny frame secured by a U-lock. Every part was stripped off it.