It seems many countries don't treat illegal imigration with the same amount of seriousness.
Although many ARE running from tyrant governments & out-of-control gangs, a lot are simply running from their legal systems.
They come into a country, illegally, they don't have a desire to learn the native language, follow the laws of the country, get innoculated from diseases, run up costs associated with their illnesses, crimes, etc ... when it gets too much they disappear back into the population or to another country.
That's the MAIN BIG ISSUE with illegals entering other countries.