>Like any other system, the purpose is what the system actually does. Especially a system that's been around for decades.

See: https://news.ycombinator.com/item?id=49260422

>We let them in, so they can work our fields and process our meat and whatever else. We shouldn't be surprised they want to buy cars, own business, and do other completely normal things.

So if the city/state/federal government lets a drug addict/dealer population to exist for too long (despite their best efforts at cracking down), they'll eventually get grandfathered in, and we can't enforce anti-money laundering regulations or dismantle their crack dens?

I mean it makes sense. Let them come and work illegally, which is much cheaper and enables proper exploitation and then blame them for all kind of things and frame them as the bad guys that exploit the society.