Woocommerce Database Relationships

Hello, I have a question,

Why tables belonging to woocommerce and wordpress don’t have foreign keys in constraints tab? Even if I generate ER Diagram in DBeaver, the relationships don’t show. Even if I export database to SQL file i dont have Foreign Keys Constraints. Can I somehow get Woocommerce database ER Diagram with relationships shown? I am student and I need that for my project.
Thank for your help.