The real reason for this, IMHO, is one of the last points of the article - No major browser has embraced it as a core feature. Getting this into say Mozilla or Safari would go a long way to make it standardized.

Also, I'm waiting for a usable "Receipt" microdata - imagine buying something, then when you get to the receipt page, it gives all the information about the transaction, ready to go into your financial management software, or into a program to keep track of the packages being shipped to you.

Then again, this may be because I hate Intuit with a passion...