I know this comes up every so often on MN and gets quite divided - all I can say is that, as much as I understand anecdotes are not data, I have never done this, and have never seen any family, friends (from school, university, other, so spanning a wide geographical area and social backgrounds), work colleagues, or other acquaintances, kiss their parents or anyone other than very young children/their romantic partners on the lips.
I've never even noticed strangers doing it outside, e.g. in shopping centres, at airports, train stations, what have you.
I have no recollection of ever seeing parents kissing children (or two friends, or DIL/SIL and PIL, or employees and bosses) in that way, even on TV or film.
If I did see two people who were obviously not romantically linked kissing on the lips I would therefore consider it highly unusual.
Therefore unless I happen to live in some strange self-selective non demonstrative bubble I can only conclude that it's one of those things that a lot of MN do but the majority of the population at large don't. Not that it makes it wrong or dodgy in any way, of course, but I would suggest that the majority of 15 y/o don't kiss their fathers on the lips - otherwise surely it would be a fairly common sight in real life/media to the extent it wouldn't even be worth noting.