If you want your business to succeed, you better have a free and open labor pool.
This is why economies grow with open borders, because it's more labor efficient.
Can you imagine not being able to hire a specialized SQL coder, because the only one available is in Austria, and you're business is in France, and there's no labor mobility?
Or did you think labor was a commodity? And that anyone can do anyone else's job?
In France, you can hire a SQL coder straight from Zimbabwe, South Korea, Venezuela or any other place on earth without a problem. The laws are in place and the EU has nothing to do with it.
We'll ignore for a minute that there is no shortage of SQL coder so it's really not warranted to recruiter from that far away. Unless it's a consulting company that tricks them to get minimum wage and resell them for more to make a profit.
We'll also ignore that they don't speak French.
There are only a few cities with a couple of jobs for them. The USA has stuff in SF/NY mostly. France has some stuff in Paris. That's about it.
We aren't part of EU, but the EU is a very appealing place to work.
The EU is simply not necessary for free trade; nor is free trade its main goal. The EU as it is right now is becoming the next Sovient Union. A undemocratic, centralised, bureaucratic superstate that strips the people from their sovereignty, independence, cultural and ethnic traditions. What the EU is trying to do has been done in the past and it has failed.