I do think you are agreeing with my post?
"there are some things on my hard drive that I want to remain private"
Agreed, but it may depend on what one regards as private. If my family choose to look at my "private" material, it matters little to me. Other things, such as bank and other security items, all require further log in knowledge, so it is not an issue (for me).
" Chances are whoever the burglar is will know little more than reinstall the OS"
Chances are, also, he will.
I am not disagreeing with your post, simply stating an alternative view. If a computer owner feels that he has sensitive data on the machine, it is always a better option to make it difficult in anyway possible. Maybe digressing a little for the thread, but you will find quite a few posts on the web, deploring Ms tightened security in Windows 8. - that's life!
In my case, having a low budget, my best security, (absurdly) would be heavy insurance or keeping the computer under lock and key when I am out. -I could not possibly afford a new computer out of my own pocket.