In 1999, we had a Polish foreign exchange student living with us for nine months. She and my daughter graduated high school together here in Arizona.
Since then, we have visited her family in Poland twice for a few days each time. Neither time did we acquire a visa. It never occurred to me to ask anyone about a visa.
The reason Poland was not visa free to the US is that they had a problem with visa overstays.
I believe nearly all the other former Eastern Bloc countries are now visa free travel to the US so this was a real embarrassment to Poland.