How many other countries police their egress borders though? When I cross a country line, I fully expect to be greeted by the border guards of the country I'm entering, not the one I just left.
Exactly. That was a favour France was doing the UK as a sign of good will, internally risking huge amounts of political capital. It seems leaving the EU will reduce the amount of good will France is ready to spend for Britain.
We are simply not in the same camp anymore.