Interestingly, the Potterverse is high on mind-affecting spells, but very low on illusions. Assuming illusions are not more difficult to cast than other spells, if artificial daylight holds all the magical properties of normal daylight, vampires and trolls should be virtually (or actually) extinct, since every wizard irrespective of combat training would need only create the illusion of a miniature sun (and presumably close their eyes or look away) to instantly obliterate/incapacitate any such creatures in a fairly large area.

There's probably something magical about direct sunlight.