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.
Wait, that sounds a lot like American...nevermind.
Funny, that's how the Mexicans are portrayed in Argentina!
Also, the ll's are also said like a soft j. That is called a "Porteno" accent.... what I learned in Buenos Aires. There is another accent that is a hoot. It is called a "canta", where the words are truly sung. It is a riot to listen to.