You're assuming everyone has a range to use at moments notice and the time to go.
The place Ishoot is an hour away,and I can only get out onselect weekends to hunt/shoot.

When I was sighting in my muzzleloader, I had a misfire and I was uncertain what the problem was.
The breech plug was frozen and required a vise to remove, thus ending my day.

With the boresighter I was able to check things out between a couple shots, and determine a baseline, especially before makingcrosshair adjustments.

This all happened a week before opening day of gun, and it rained on Sunday...I would have been screwed big time w/o the boresighter.