I'll give you a bunch of reason too :
afk
brb
afk food
afk bio
forgot a step in my quest brt
I just hit level XX, I go back to Ulda to get my new weapon
afk someone's at the door
etc
etc
etc

The day people will respect their PTs, they will get a bit more respect (perhaps) from other players.
To explain a bit further, when i have only 3hours to play, i hate it when people go afk for a thousand reason... I am not from Japan, but i guess this is a reason why they dont want Western players when they can.