the only reason I can think of is that the location you want the fire to start is hard to get to, or at least hard to get to without being noticed. at that point, you have several options: crash a plane into the area, fire a missile into the area, pay a Fall Guy to commit arson, or use one of your lasers. of all these solutions, especially given the demonstration in the video, the laser would be the most likely to go unnoticed.

of course, all of this is just thinking it through logically. in the end, a simple match is a much cheaper and direct solution.