Working on site with no lighting, halogens are commonplace, especially in winter with short daylight days. They are brutal for showing defects. if you take them into private homes where you want a really good shot at finding all the defects in a wall, it is absolutely a good idea to have the halogens blaring too.
Some of the kitchen painters do carry a light for final inspections after filling or before final coats.
Not a bad idea to maybe run a halogen over the walls at the start of a wall painting job, to see if there is anything wrong with the walls that may show up that one day a year when the sun is shining at a certain angle.
Came across this recently, a beautifully prepped and lined and painted wall, apparently you could see ripples in plasterwork or studding at a certain hour on a certain day of the year. It all felt smooth and was ding free, nothing more a decorator could have done with the wall, but letting the client know that the wall was badly built from the kick-off may have managed expectations.