In the case of the Sprints, there is only one manufacturer, one business that assemble and market them, one sailmaker. Everything can be bought off the shelf. There is very little scope for manipulation of the rules, so a certificate is not necessary. This is an attractive feature of the Sprints!
In some classes, the position is different. Finns, Albacores, Solos, Dragons, and many others will have different suppliers. Indeed, some boats are made of wood, fibreglass or composites. There can be different suppliers of sails and masts. In such cases, a measurement certificate is a necessity. Not so, with the Sprints.
Moreover, whenever you enter a race or sign a declaration, you are confirming your boat conforms to class rules.