Thank goodness monitors and beardeds and geckos and chams do not need it. As Those bulbs(reptile UV bulbs) Are mostly useless buy their own instructions. Most only emitt what is said to be effect within a few inches of the bulb. Then normally stop doing that within a month or so.
I would research those bulbs if I were you. Not research if its needed, but research the bulb itself. Maybe buy a UV meter. If you did that, you may find out those bulbs are no so effective.
I have raised more monitors from the egg then about anyone in the world(an educated guess) I never used UV bulbs or the sun with babies. A quickly growing baby has more need for placed calicum then at any other time in their lifes. I do not have calicum problems with them or any monitor.
I have also done that with chams, torts, turtles, beardeds, all manner of reptiles.
Is it useless, if you said you use it because it made your animals look brighter, then theres a use. Actually You would be better off with two florescent bulbs, One grow bulb(red) and one sun(blue) that would duplicate the sun very well. And its far far cheaper.
The other use is, Petshops got to make money somewhere. Cheers