Then problem comes when 1000s of Eastern Europeans move into your town and don't want to Assimilate! They make their own less attractive neighborhood. Some bring gang crime, like moving from Mexico to the USA with millions and millions of Latin gangsters now. LA, Fresno, etc.
Fewer local shoppers means fewer local shops. Kind of like the big box stores and huge malls destroying town's tiny downtown thriving businesses, like novel Valley Fair and downtown San Jose, Redev. Agency costly criminal mess, and still SJ is struggling after city govt moved out and back, and crime peaked. Beside pampering BigBiz to detriment of resident citizens and their neighborhoods, SJ is still a mess. Sanctuary City anyone? East San Hosed.
Western Europe, like SF, depends on tourism.
If you fly to Italy or Austria, France or Sweden, do you want to meet locals or unhappy unassimilated 1000s of uncivilized bad habit possibly unprincipled or criminal Eastern Europeans?
Western European country cultures are so different and still not ready for EU no borders.
That's why since the 1960s the EC or now EU has had trouble talking about this aspect of the human not biz huge social experiment.
