[thin_carapace]

probably because society does not provide a manual on behaviour and ethics but religion does? and more people nowadays are getting sick of how the 2 default human values of pleasure/pain are systematically used against them? and once you join a community its nice to add new members? regardless as to any of those answers it's been acceptable to openly proselytize atheism on the internet forever, bit hypocritical not to allow other religions to do the same.