Outbound Glossary
Data minimisation
Holding only what you actually use. Enrichment makes breaking this rule frictionless, which is exactly why it gets broken.
GDPR expects you to collect no more personal data than you need for the purpose you stated. In practice that means a field you never use in a message or a decision should not be in your database.
Enrichment tools return everything they have, and it costs nothing to keep it, so lists accumulate personal details that serve no purpose and would be embarrassing in a breach or a subject access request. Deciding which fields a campaign genuinely uses, and dropping the rest on import, is the cheapest compliance step there is.