Depends on what kind of bread. Mass-market sliced bread in a plastic bag? The butts are only good for keeping the next non-butt slice from drying out. Vanishingly rarely, I’d use them for breadcrumbs.
Baguette, ciabatta, or artisanal homemade bread? Butts are less desirable but still enjoyable. Good for dipping in soup.
Hee. We got PB&Js every day of our elementary school lives (except for that one glorious bologna sandwich day, but I digress). Normally it would be two slices of white bread from the used bread store, store brand grape jelly and PB from the store brand five-pound bucket, in a regular smallish brown bag.
You knew it was shopping day when the sandwich was two butts, PB and no jelly, and the bag was a shortened cigarette carton bag. 
Me? No
My husband? Yes
Nope. I’m a diabetic and have to be able to make some kind of WAG as to how many grams of carbohydrate are in everything I eat. My assumption is that the heels don’t really match up with what’s printed on the label as far as that goes. Sometimes I’ll even skip two or three slices so that I get something that’s more like an average slice.
Mine call them the Bread Ass.
Love them, and I like the crusts on the middle pieces too. Always drove me nuts when I went to visit friends when a kid and got sandwiches with the crusts cut off.
And as an oddity, my favorite sandwich growing up with the square liver loaf with the rim of fat on toasted white bread with mayo and lettuce, the only sandwich I wanted cut in half so I could eat the inside first and save the crust with fat rim for last. Very Germanic - I also like the thin sliced cured fat, and chicken, duck, goose or beef ‘dripping’ smeared on toasted bread.
I grew up calling them “the crusts” but learned to appreciate calling them “the heels” because that just makes sense: every slice has some crust.
For me, the heels need extra lube.
Of course, it’s the best part. But then, I also eat apple cores, banana peels, lettuce hearts, etc.
I grew up with a depression-era mommy who didn’t waste anything.
I’ll only eat the heels if they’re nearly as thick as the rest of the slices.
Toasted.
Yes, I do eat them. The taste is slightly different, but on this point I’m not fussy. It seems to me the heels do keep the next slices a bit fresher. This was more important before the advent of plastic bags, though. The waxed paper bags were harder to seal, and in our house the heels were almost totally stale by the time we head eaten the rest of the loaf.
Indirectly, after I pulverize them in the processor and add them to meatloaf.
Damn straight (although of course I know you meant to say Marmite 
).
When they’re toasted, they have a concave crumb-face that allows them to be loaded a little more liberally with butter, Marmite, and I like to swirl a little bit of Sriracha sauce into it too. The crust side prevents the butter from soaking right through and dripping down my shirt.
It takes me a while to get through a loaf of bread as I’m a diabetic, so I keep the kantapää (finnish) in place to keep the loaf fresh. But they’re the best part.
Store bought bread, I keep them as “bread protectors” for the rest of the loaf, and then toss them when they’re the only pieces left.
On homemade bread, they’re the best pieces, and I’m lucky if I get one before someone else snatches it.
I do on sandwich bread, but not on baguette or ciabatta.
I am often tempted to but I usually save at least one (the second) for one of those days when I really need a lift. Crust is my favorite part of any kind of bread so heels on a white loaf (around my house) are MINE ---- ALL MINE.
I love bread heels. When we order heroes at lunchtime, they don’t get one for me. I’m happy eating the ends that nobody else even wants.
Not while fresh. I usually let them go stale and make bread dumplings once in a while.
For really crusty bread like a baguette it is the best! For regular bread I still eat it but usually as toast. I wouldn’t use it for a sandwich. It feels weird.