laser erases graffiti

A laser device selling for about $80,000 US will safely erase pen and spray paint from Italian monuments. It takes one person about 20 minutes to erase an area of 10 square centimeters, about 1.55 square inches. 

Seems the pen is used across the world, especially at UNESCO world heritage sites. 

I have to wonder, though. The monuments made of stone...would soap and water be easier and still safe to use? If it's made of stone, would a pressure washer occasionally used be ok? 
I do believe that it is important to save artworks and monuments from graffiti and vandalism, but is this the best way to save artworks and monuments from graffiti? 

What do you think? Read the entire article here:  http://artdaily.com/news/111881/World-s-first-graffiti-busting-laser-helps-Florence-s--Angels-#.XIY_HCJKi70

Sprinkles and Carousels with Aqua Girl with Yellow Circles, 22 x 8 inches, collage on paper ©2019 Angeline Marie Martinez