Hoovering up the Eastern European countries, as the EU have done and would still do, obviously meant, that being poor countries they could settle anywhere with or without a job to go to.This has put enormous pressure on a few countries, especially the UK.If it had gone on and on who knows how that would affect the UK.
That is only one aspect of us staying in the EU btw.One that we can easily identify, with the free movement of labour.
Other nations are uneasy about EU diktats and are already disregarding them in some cases.