Because they are children (or childlike) and they think, like a lot of
childish people, that swearing and trying to shock and annoy others makes
them look grown up. Whereas we grownups just see them for what they are,
silly children.
--
Regards
Bob

They will probably grow out of it by the time they reach their teens,
unfortunately they are likely be replaced by an endless succession of
similar kids posting inane ramblings.

David.