I don't think I encrypt my drives and the main reason is it's usually not a one-click process. I'm also not sure of the benefits from a personal perspective. If the government gets my drives I assume they'll crack it in no time. If a hacker gets into my PC or a virus I'm assuming it will run while the drive is in an unencrypted state anyway. So I'm assuming it really only protects me from an unsophisticated attacker stealing my drive or machine.
Please educate me if I got this wrong.
Edit: Thanks for the counter points. I'll look into activating encryption on my machines if they don't already have it.