And then I opened a fridge once, told to find a bottle of wine chilling there, and I realized that nectar of gods comes in PET bottles here. Surprisingly, it tasted better good average wine and with years of living in Czech Republic I stopped being terrified about the the idea.
Explanation is quite simple. As unique, exquisite and old wine always comes in traditional, noble, narrow neck bottles, lots of normal wine for every day drinking is being tapped into plastic in little shops and wineries all over the country. This way it's cheap, abundant (1,5 liter in minimum purchase) and more mundane.
That's a way of Czechs saying - we have good, cheap wine that you should sip every evening and let's not get too snobbish about that.