I rarely give my chickens the heel off the loaf of bread. I didn't give them any of the hotdogs I threw out either. Those items went into the compost bin.
If we get to the SHTF scenarios, I will. But we're not there. Actually, if we get to that point, there will not be any heels of bread or hotdogs to throw out, as we will eat them first. And if we get to that point, I won't be so picky as to turn up my nose at, say, raccoon or possom or groundhog. (None of those sound even remotely appealing to me, but I've never had the opportunity to eat them, prepared by someone who knows how.)
Commercial feed is easier and cheaper than trying to feed my chickens on what I can grow or find for them. It's almost certainly better at meeting their nutritional needs too. I don't stockpile bags of the stuff because it does have a shelf life.
A year or so ago, there was lots of chatter about how the war in Ukraine was going to lead to shortages of grain and therefore feed. I asked the owner of the place where I buy my feed if he'd heard of that, and he said he had not.
He could have said, "You better stock up now, because I think there will be a shortage," and tried to sell me 6 bags of feed. He could tell me that any time I'm in there, but he doesn't. He's in a better position to know what his supplier has available than I am.