Because casual games are the ones that attract kids and adults alike which means casual games are what we could say the Everyone rating games. Space invaders and Pac man was really a casual game so even young girls actually playing it, infact, most of the one playing these games the old arcade ones are mostly young girls.
About FPS, again, theyre really casual game so even teens not only adults could play it. COD 4 are played mostly by teens even with the rating it got the more reason why Mature games are always subjective.
end of core gaming days prediction:
E3 2006-The beginning of the end. Wii introduced
E3 2008- Armageddon. Wii motion plus introduced. Wii Music. Reggie says Animal crossing was a core game. Massive disappointment. many Wii core gamers selling their Wii.
E3 2010- Tape runs out
http://www.fivedoves.com/letters/march2009/ICG_Tape_runs_out.jpg
