Don't know if it would really be more convenient since then you would have to remember to scan the items when you use them, or at the very least when they are done. If you forget to scan them when they are finished you'll get warnings about food that is about to expire that you already ate. And you probably want to scan the food every time so it can nag you to use the other package as it is going to expire sooner. No thanks, I'll pass on that.
And for having things like the Nest memorize my behaviour in order to save me some money. It's a nice idea in theory but I don't like the practice. Chips are powerful enough that they don't need to send my data off to Google to perform that analysis. If you want me to pay $250 for a thermostat then my data stays with me. If you want my data then give me the thermostat for free. I know they are making money with that data analysis or else Google wouldn't have spent $3.2B on Nest.