The licence, shows that you have passed a medical, and includes a certain amount of insurance, how much, I don't really know.
It also gives the governing body a lever to control things, ie, refusal or disqualification of the licence if there's repeated issues with a racer, so it simpifies exclusion if it's needed.
The measurement certificate is to show that the boat complies with the rules specific to the class in which it is to race.
A new, or rebuilt boat obviously needs 'measuring' to confirm that it fits the rules.
The issue of repeat certificates, which are just posted to the boat owner, on reciept of a yearly payment is a little more confusing, if the conformaty is not actually tested before re-issue, and the certificate is mearly posted, it's only really about colecting another 'tax' for the priviledge of racing under RYA rules, in other words, a load of bollox!
"I Agree with everything you say really!" - John Cooke to Jon Fuller - 26-01-2013