I've heard this over and over, and I totally understand your concern. But I think there's at least one reason to stay on Coinbase though, and it's their insura

I've heard this over and over, and I totally understand your concern. But I think there's at least one reason to stay on Coinbase though, and it's their insurance against security breaches, including employee theft (note my comment above). I'm not individually insured against bitcoin theft, and I also think there's a non-zero risk of making an irreversible mistake with my own offline storage. I'm not incompetent, but I can't claim mastery of the bitcoin protocol either, therefore I assume I can mess things up. So yeah, you don't get your private keys, but insurance on your full balance is worth something to some people, in some cases far more than the assumption that nothing will ever go wrong with your own wallet (if you feel comfortable with that assumption, great).