I agree with the general comments about the jackets improving safety, but it can get a bit ridiculous. On a recent trip to an international (just) airport in the North East on a private flight, we were sent to park on the apron. No instructions were forthcoming on how/where to get into the terminal (no sign of the big black C, as I remember), so we set off, past the baggage handlers, and finally found a way in. There we were met by Mrs Jobsworth who told us we would not be allowed back out to the a/c without at least one of the required fluorescent vests. The fact that we had walked across the (deserted) international apron without said vest and without being chopped into a thousand pieces seemed irrelevant. The only way out it seemed was to buy a vest. I explained that we would only be stopping for lunch and enquired whether when we came back there might be someone available to escort us the 50 or so yards back to the apron. "Oh no," came the reply, "we're far too busy, and we've an international flight due in half an hour." So we bought one of the vests and had our lunch in the company of the other half-dozen people in the terminal. In the meantime, NOTHING moved on the apron. As we taxied out, said international flight was just shutting down: a KLM/UK FK50. Mrs Jobsworth was still ensconced in her little cubicle as someone else (in yellow jacket) prepared to meet the flight.
Amusing in hindsight, but bl**dy annoying at the time, and not really seeming to further ramp safety any.