Devil's advocate: My wife thankfully just got her green card three months ago. She first came on a J-1 and then an F-1. She knows many, many people who come with the intent of staying either without status or via questionable marriage licenses. The vast majority of her acquaintances in the J-1 visa program were young (<25 year old) au pairs with no intention of learning English (they had 'mandatory' English language cultural lessons per J-1). My wife is an extreme outlier in that she learned English in 5 years and just got accepted to veterinary school in USA.

The bottom-line is that she thinks the J-1 / au pair program should be discontinued.