You Know What Would Be Even Funnier

Using email as a primary key is already a terrible idea—what happens when users want to change their email? Cascade updates everywhere, foreign key nightmares, and a database migration that'll haunt your dreams. But sure, let's one-up that disaster by using the password as the primary key. Nothing says "job security through catastrophic technical debt" like having to update every single reference in your database when someone inevitably forgets their password. Also, you'd be storing plaintext passwords, which is basically a resume-building exercise for your next gig after the data breach lawsuit.