Why do foreigners come to Australia if they don't want to imilate into mainstream Australia?

Australia is much better than the countries they left - particularly war torn ones. It's a shame that they don't get over their former lives and have to re-enact it here in oz. You'd think that these people would be so happy to be in a peaceful environment. The increase in racist attacks will escalate in the future due to this not letting go of their pasts.