"Have a great summer!"
Among the problems that arise from tourists sexually assaulting a tombstone is the fact that the monument is porous, which means lipstick grease sinks right into the stone itself. Groundskeepers wash the monument, more dummy kissers show back up to slap their saliva right back on it again. Decades of kisses, cleaning routines, and still more kisses have taken their toll on the tomb, degrading it to the point that repairs were utterly impossible. Left with no other choice, authorities instituted a fine of 9,000 pounds (or $12,000) to be issued to anyone caught doing the deed and idiots are still making out with the rock.
Eventually, the people in charge of the gravesite removed visitors' ability to spread their cooties all over the final resting place of a literary giant altogether by creating a glass barrier to discourage further PDA. Naturally, the glass barrier itself is now covered with the heartfelt platitudes left by visitors of the tomb. Maybe if the right kisser comes along, Oscar Wilde will revive himself like an Irish, dandy Snow White.
And this is why we can't have nice things.