If the UK is no longer an integrated part of the European Market, then we're no longer a logical base of European distribution.

That means if you want to sell stuff across Europe, it doesn't make sense to employ people in a UK that's outside the main European market.

Every Market has trade barriers.
If you wanted to sell across Europe, and you were looking to set up a factory in either an integrated Single Market which covers 30 European countries, with 500 million customers, or a market of 65 million customers, where would you put it?

Concrete example:
You own Nissan.

Nissan's Sunderland factory sends 70% cars to EU countries.
A trade barrier between UK & EU means 70% of your cars face extra cost.
If your factory was on the other side of the barrier, it'd be 30%

Where do you put it?

And if you make the obvious decision... what happens to the 34,000 people across the North-East who depend on the Sunderland factory's supply chain to put food on their family's table? https://news.sky.com/story/nissan-warns-on-serious-implications-of-no-deal-brexit-11516957

Now yes, there are examples of UK-based businesses using EU rights to move to other EU countries, but I'm asking you to use your own head and think:
Ask yourself whether jobs are more or less likely to come to the UK if it's an integrated part of a larger market.

The Brexit people voted for was the one they TOLD us they were voting for! The one with no tariff or non-tariff barriers to our largest and closest trade partner.
That's what that Nissan worker (above) voted for.

Shame on ANYONE trying to force something else on him!