[scoot]

Because Brexit wasn't a consideration in 2014. Even if it were, EU regulations that come into force during the notice period, or in the case of the U.K., a further 2 year extension period are still applicable.

Take GDPR for example. It's protections will apply to UK citizens, just as any other EU citizen, from May 2018 until such time that a) the notice period and extension period have lapsed, b) the UK government subsequently rescinds or replaces the relevant legislation.