Can only speak for our industry RainyParis with any real knowledge. We are in the construction industry.
An influx of cheap labour from the EU, primarily Eastern Europe means that prices have dropped. Gangmasters run huge gangs of men, lodge them in shared houses and flood contracts. Because the cost of living of these men is less than someone who permanently lives in the UK with a family, and because of the numbers of unskilled labour it drives prices and the skill base down. We pay a new labourer around £10 per hour, rising to £12 when they have the basics. Some skilled fixers are working for that. We pay skilled fixers between £15 to £18 per hour. To make any profit we need to charge £19 plus per hour.
We can't compete with the big gangs. We aren't the only ones.
In other industries I expect it's similar. It's OK saying that people won't fruit pick etc but many cant afford to and maintain a home in the UK and support a family.
DH working for his £15 per hour has a home in the UK to support. Someone from Eastern Europe may be paying £30 a week lodge then sending money back home to wherever in Europe he was from where the cost of living as a family is a lot cheaper, and benefiting from the previously strong £ to the €.
Since the £ has fallen and since attitudes have changed since the Brexit vote, work and prices have picked back up again. Anecdotal I know, but we are certainly doing better this last 2 years than the previous 5. Obviously we were in a recession then but DH says there are far fewer eastern European gangs on sites.
I know immigration and migration has a positive impact overall on the UK and the economy and we need it. But in certain areas and communities and industries it hasn't always been positive. And that's why those communities blame the EU I would imagine.
Cheap labour from the EU is good for places like London where there are a billionty jobs. But where employment isn't as good and the playing field isn't level (ie cost of living not equal meaning people from certain countries are better off than the UK workforce) you will get resentment and a leave voter.
I reluctantly voted remain. Many people I know reluctantly voted leave for the above reasons.