In Paris, ubiquitous couples mashing faces on park benches spend much of their time glancing around them to see who's looking.
Without an audience, apparently, what's the point? In Prague, not generally considered one of the world's friendliest cities, teenagers in each others arms on crowded streets appear to notice no one around them.
There's a lot of public kissing in Moscow, too, but recently it seems to have reached a new level.
Returning there after a year's absence this week, I was struck as visitors always are by fresh evidence of Russia's oil wealth: construction everywhere, more super-luxury cars jamming the streets than ever before and endless streams of intricately coiffed women in the micro-miniest of skirts on their way to extravagant all-night restaurants and nightclubs.
But this time I noticed every establishment I visited -- including my old favorite Georgian restaurant, the outdoor veranda of a Philip-Starcky lounge, and a sushi place serving a bustling lunchtime crowd -- had at least one couple actively using tongues for neither eating nor talking.
In a place as gritty and cutthroat as Moscow, appearing you have no care in the world is an attribute of success more than in many other places.
So it was with molls in extravagant designer dresses smooching men with crew cuts and wide open collars looking capable of beating someone to a pulp or pulling a major heist.
In one restaurant, a blonde in a little white dress draped her legs over a dark-haired man with chiseled features and a pinstripe suit sitting next to her.
Both evidently in their mid-40s, they peck-kissed each other with the tenderness of a new high-school couple. It was touching. Really.
Leaving afterward, she could barely negotiate a ripped-up sidewalk (the asphalt of all downtown pavements is being replaced with bricks) in her teetering stilettos. But overcoming the odds is the key to success in Moscow.
And once you do, it's all about your maximum enjoyment.