Because they're hopeless, with third world mentality. Always hand out, high crime levels, corruption. And instead, they come to free load of the clever, industrious, generally law abiding white man rather then trying to make a go of it themselves. Well, the way we're going with numbers arriving, our stable European lifeboats will soon capsize under weight of numbers of useless breeders. Just like many African countries.
Some examples.
South Africa - they've had over 30 years of freedom and were bequeathed a modern infrastructure by the white man. Murder, rape, robbery, car-jack, etc, etc is through the roof. Natives strip the copper from power lines then complain because they have no power. Coruption is endemic. This means they have not invested in maintaing things like power generation - and they now have regular, daily power cuts all over the country. Instead of a success, SA is now a basket case going down the tubes. SA Rand has much less than half it's value compared to pre apartheid.
Haiti - had independence for 200 years, Yet again it's a stinking, crime-ridden hell hole. How many centuries do they need to get their act together?
I could give many examples of African and Asian run countries that are the same. Lefties love to patronise the ethnics by blaming the white man for their hopelessness - reality is they are masters of their own downfall. They can't blame the resourceful industrious whites for their situation of crime, war, corruption, over breeding when the white man gave up control of their countries decades or even centuries ago. That's just dishonest. They're just not suited to a modern first world environment.