At first, slip coaches were locked away from the rest of the cars for safety, but the populace demanded restaurant access for their multiple nightly cocktails, so they built new coaches with corridors. That meant the guard had to ensure everyone was present during the decoupling, in addition to the already-stressful job of steering a literal runaway train. Had to use the loo? Too bad, you're going to Brighton now.
Amazingly, in over 100 years of service, slip coaching resulted in only two serious accidents and zero fatalities. But slipping required extra workers, slipped cars could not be quickly reattached, and trains became dangerously faster. So on September 9, 1960, the last-ever slip car pulled into Bicester Station. It was probably muttering about nanny state party-poopers, like a libertarian Thomas the Tank Engine.