And anyways, people can impose some sort of hunger system on themselves. It is a roleplaying game after all. If you think you've been out in the wild too long and Geralt may be hungry then go to the local tavern. .
That of course depends if they allow food/drink as edibles that you can consume at any time. I know they did mention it in the Q&A video but they never specified how and when the edibles could be consumed, so it might not be a situation where you can do it at any time, but I hope so.
I'm all for people doing just what you said and implementing roleplay mechanics on themselves, and I think that's a better option than forcing everybody into something tedious like a hunger mechanic. However they need to at the very least have the system in place so people who want to, can and sadly being that it was removed in TW2, hopefully it's back and in its full glory like it was from TW1.