As far as I know, this piecemeal approach to the amassing of safety-related legislation applies also to the railway industry in this country, since so much of the Rules and Regulations on the railway has come about through recommendations and requirements from safety enquiries after accidents.
It could, I'd have thought, be argued that that approach lends strength to the safety regime in the industry, but it does mean that the comprehensive and accurate picture relating to any particular instance is hard to divine. Thus, legal experts are needed both to interpret and to test the legislation.
Having taken this approach, and used it to form a considerable bulk of regulation, in both industries, it would be hard to replace it with a complete revision, I suspect. In any case, under our system of law, it would require a great deal of testing in court to arrive at a situation where a revision could be regarded as reasonably watertight. That, at any rate, is my layman's feeling on the matter, no doubt expert opinion will portray a more accurate view.