Because that was the official government line?
Channel 4 news went to an area where there was a massive divide between immigrants and Brits and asked why there was such a problem; both sides (basically) said they had a right to be there and therefore a right not to have to make an effort to integrate.
It might be an idea to control where immigrants originally settle once they're in the country. Different areas have different needs and some areas struggle to handle it's existing population let alone competition for attention.