Graffiti is one of those things that has endured over the ages, will always happen no matter the methods put in place to stop it. Some of the stuff they have found at Pompeii for exampleThere were (probably more) idiots and vandals back then than now...the only difference being they had chisel tips, and now they have sharpies.
Vandalism can be removed, repaired and quickly treated, the vandals will be in the queues more likely than the towers, and the shaggers will still be in the bushes and gardens, I remember the grass "ride" of picnic tables up to the side of the corkscrew in my youth...the picnic table bays were often very "busy"...sex drugs and rock and roll.
The Towers ruins in comparison were cool, quiet and respected by pretty much all.
Proper stately stuff.
And me.

The Bawdy Graffiti of Pompeii and Herculaneum
Everyone is now familiar with the release of quite explicit photos and service charges found on the walls of a brothel excavated at Pompeii, the resort town destroyed by the eruption of Mount Vesuvius in 79 CCE. Now for your viewing pleasure comes a list of bawdy graffiti scrawled on the walls...

Maybe in a few hundred years archaeologists will be wondering why the towers ruins have “gyat rizz” carved all over them.