I don't think it is everyone being self centered, albeit there is an honest few out there.
People just want to share what they've done or experienced.
Odds are they aren't 100% of the time "LOOK AT LOOK AT ME LOOOOOOK AT MEEEEEE"
They just want people's opinions I would think.
As for the "Older members don't use grammar" Older members tend to stop giving a stuff; Thus slacking off in their grammar because all they want is enough to get their point across.
so if they dont use grammar its either to prove a point, or because they dont give two hoots if you "correct" them