Why do we kiss?

Kissing is one of the most common romantic behaviors. In fact, 90 per cent of cultures around the world do it, research has shown. So you'd expect researchers studying romantic relationships to understand why humans are so into kissing. But it turns out there's still a lot they don't know about smooching.
One group of US researchers decided the time had come to learn more about why on earth we do this weird thing to each other with our mouths. They were interested in people's motives for kissing, including their goals, desires, and needs. They were also keen on finding out whether these motives were different for men and women, and if other things like age, relationship status, and personality made a difference.
'I couldn't resist!'
They tracked down 461 people aged between 18 to 74 and asked them to fill in a long questionnaire on reasons for kissing, called the 'YKiss? Scale'. The list of reasons is divided into two categories, Danica Kulibert, one of the study's researchers, told Love Matters. First, there are 'goal-attainment motives', which means kissing for a reason that has nothing to do with romance.
Those are things like, "I wanted to get a promotion" and "I wanted to defy my parents",' says Kulibert. This category also includes goals that are not exactly positive, such as. 'I wanted to get even with someone else' or 'I wanted to hurt/humiliate someone.'
The second category is called 'sexual-relational motives'. These include the romantic reasons for kissing you'd expect, like 'I wanted to set the mood,' 'I wanted to express my love for the person' and even 'I saw the person naked and couldn't resist'! Pleasure and affection
At age sixteen, most of the participants had their first romantic kiss, the researchers learned. Fast forward to their adult years, and the average number of kissing partners was about 20.
So it's not too surprising that the most popular reasons for kissing were in the 'sexual-relational' category, all about pleasure and affection. This was true for both men and women, who were equally into kissing for romantic reasons.
Getting what you want
Want to take a guess who does the most kissing just to get what they want, and not for romantic reasons - men or women? Men! They gave all sorts of reasons for kissing that had nothing to do with romance, including some surprising ones like 'I wanted to get out of something' and 'I wanted the person to stop bugging me', or 'I wanted to enhance my reputation'.
Why are men more motivated to kiss for reasons like these? 'We don't truly know why,' Kulibert says. 'We can speculate it might be because society tends to draw a picture that men are in charge of initiating sexual behaviours.' This could mean that, in general, men kiss for a much wider range of reasons than women, and that goal-attainment motives are only one of these.
Top 5 Sexual-Relational Reasons for Kissing