high vis jackets are a health and safety requirement and should be worn when not on a designated path at uk airfields where h&s have deemed it nesecarry.
as an airline pilot can i tell you its quite dangerous these days doing a walk round with engineering vehicles, catering vehicles, fuelling vehicles etc on the ramp, i was nearly run over a few months ago at heathrow by a reversing baggage truck in low light.
when i come onto stand its also very important, especialy in low light, that all personel around the a/c can be seen these jackets are great in that respect.
i appreciate that as private flyers it can be a pain but discipline and regulations are an essential part of flying and are needed to ensure we all go home in one piece every night!