In my country particularly in rural areas (not cities) it is a sign of respect towards more elderly people or if you're a child towards adults. When I moved to another city I greeted the mom of a friend I used to study with this way both when I stepped in and when I leaved her house and with a little laugh she noted that this kind of thing was not a custom there. It also a greeting and a sign of respect in mafia households to the point that if you don't do it for particular ceremonies you're risking a lot because it means you're actually opposing and disrespecting the person you refused/ignored.
ooh its funny how every country has its own greeting but with similarities! france is really famous for its greeting and its so common that i get use to it but i can totally understand the uncomfort! and « beijinho » is such a nice word, portuguese is such a pretty language i wish i can learn it somedays!
i love this stereotype japanese people have that foreigners just randomly go kissing people like bro WHERE i mean yeah depending on the country/culture it can happen but literally NO ONE goes kissing people theyve never met before on the street thats NOT how it works