Because UK is not made of libertarians who were under the EU opression but all those EU laws were made with UK's contribution and input. The UK has not become the libertarian utopia and will not become the libertarian utopia inside or outside of EU because the British public at large doesn't want it. If anything, probably the Labour party will win the next elections, the libertarians are very unpopular. British are not Americans and most don't trust corporations and want government involvement in protecting them against wrongdoings.

Brexit's biggest con was that EU is some 3rd party and the British public wants something else. In reality, Brits made the EU.