A compliant system may or may not yeild quality products, but any organization with the objective of long-term survival must DO the things the standards require well enough that they become and remain competitive. At best, it is a statement by a credible, independent source that your system is compliant.
Registration IS something vital to firms whose competitors all have it.
The only people who believe otherwise are either registrars or consultants who always advise their clients that they need to be registered, whether or not true.