Outlook Email Receipts

I can't believe some people still use the "email receipt" feature in Outlook.  For those that don't know, it's that feature that prompts you to send the sender an email receipt that proves that you opened their email.

If you send an email to John Smith and don't get a receipt back, did he not view the email OR simply choose not to send you back a receipt? Definitely not a solid mechanism for measuring email view counts.