It think it’s because there is such a large number of Italians and their descendants there. But it could be the Portugese, too, which always sounds so sweet and gentle to me. The gentleness isn’t there in the Argentine accent. There is an actor named Juan Soler who has mastered neutral Spanish so he can work anywhere, but I have heard him revert to his native accent, with a wink, and it is a glory to behold. He has had me rolling on the floor laughing. In the Mexican media, their Argentine hermanos are depicted as huge-nosed goofs with horrible hygiene and a tendency to scratch their nether regions in public.
The Brasilians say that the Argentines are “a bunch of Italians speaking Spanish acting like they are British.”