Why does he only kiss me goodbye?

Me and this guy like each other but we're not dating, although we are more than friends. Normally with a guy you'd just kiss whenever, but he only kisses me at the end of one of our meet ups, like a goodbye kiss? I think I'm the only girl he's got this close to going out with, and I don't think he's has a proper girlfriend before, so could this be a reason for only kissing me goodbye?
Why does he only kiss me goodbye?
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