There is was no deportation for citizens of Mercosur. So, to apply for a residency was optional (I'm not updated about this as soon as I do not do Immigration law).Agreed, especially since a lot of them are Bolivians anyway, who technically can legally get residency at the drop of a hat due to MERCOSUR, they just haven't bothered with it. I have a couple of acquiantances who are Sengalese as well (no idea why they chose to come here still but anyway...) and they have no practical way to get legal status but would love it. If you're not going to deport them, as the authorities here have been reluctant to do for decades now, why not give them residency so that they can get bank accounts and perhaps start paying taxes?
The National Constitutions does not accepts the legal residency, in fact, arts. 14, 20, 25 and 28 abolish it.
The legal residency is a simple pass alike the passes we see now in quarantine.
It is a medieval military system when people was attached to the land as serfs.
Its origin is in the Quran where it is called halal (legal) while in Christendom we talk about inhabitants. The legal resident is who submitted to the sharia and it is the evidence of a partial conversion to Islam (Sura 9:29).
As far as Argentina has freedom of religion, Mercosur citizens can choose to apply or not. And you can choose between two apply as a halal resident or to citizenship as an inhabitant, a category you find in the Bible.
In recent times the III Reich was, also, a community State, racial instead of religious. The legal residence was the probe that you belong to the ethnic community. It was a racial certificate.
For the local nazism, the Argentine superior race was a blend of native (Spaniards married native women and / or had harems), Spanish (mostly converted judes), Italian and French and this is why you cannot apply for legal residency so easy as Mercosur Citizens. Meanwhile you look down on Bolivians because most of them are native Americans, the rule makers despise you as undesirable migration and privilege them because they brothers in blood.