Aha... because there's a difference...
8-12 is the first interval, IMO, when kids discover games and are actually capable of understanding them (depends on the game, of course), but not all are interested in forums
then, 12-15 is the age when kids discover the opposite gender, and that, sometimes, affects their interests in gaming
above 15 to 18, is the troubled age... we've all been there... no need to go into details

also, this is when forum activity starts to make sense... mentality is changing, also the need for intellectual challenges and social bonding
then, 18-22 is the age when some go to higher education, others just get a job... this also affects their availability to play games...
above this, the vast majority is employed or involved in a revenue generating activity and the only thing that matters is the age... above 30 the middle age crisis starts showing its fangs etc.

Retired, but still loving it.