>As opposed to just not encrypting their data at all and letting everyone who ends up with the drive have their data.
You are presenting a false dilemma where either Bitlocker is in use or the drive is entirely unencrypted; there are other ways to ensure data integrity in the face of physical compromise.
1. It's not a false dilemma, it's more of a question of how to handle the "average Joe" user that doesn't know how to store encryption keys. I don't like how this automatic encryption is implemented, by the way, but sending the keys to MS servers is not the worst idea ever.
2. Bitlocker can totally be used without a MS account and without sending keys anywhere and without TPM... But seeing how most people fail to RTFM we're back to point 1.
So one scenario, everyone can access the data if they get the drive. The other, the government might get Microsoft to release the encryption keys.