"The Adjusted Refusal Rate is based on the refusal rate of B visa applications. B visas are adjudicated based on applicant interviews; the interviews generally last between 60 and 90 seconds.[20] Due to time constraints, adjudicators profile applicants.[20] Certain demographics, such as young adults, those who are single and/or unemployed, almost never receive visas.[20] Adjudicators are evaluated on how fast they carry out interviews, not the quality of adjudication decisions.[21] The validity of B visa decisions is not evaluated."
It's 100% because in the 90s after the fall of communism a lot of people travelled to US on tourist visas and stayed permanently(illegally). It's still being used as an argument by US to exclude us from the US Visa Waiver program, even though nowadays in 2019 you'd be hard pressed to find any Pole interested in emigrating to the US for unskilled work. The risks are huge, the pay is not great, and you can hop on a 4-hour bus to Germany and work there visa-free for much better money, while having full access to healthcare, worker protections and essentially 90% same rights as a native citizen. Why would you risk going to US and overstaying a visa to what, pick strawberries? That made a lot of sense 25 years ago, when even the most basic of basic jobs would pay 50x better than any job in Poland, but that time is long gone now. Not only our salaries are better, but the entire EU market is open to us without limitations. It feels like US still lives in some kind of bubble where they believe that America is a dream land and the second Poles get access to the Visa Waiver programme they will come in droves and stay - I think they are hugely mistaken on that point.