I’ve be musing about something so mundane, that this is the only place I dare mention it.
Why is it that bread, in most cases, is perfectly acceptable and enjoyable in sandwiches and for lunch or dinner, whereas toast is the custom for breakfast?
I have tried untoasted bread for breakfast, and it just ain’t right at all.
So, why IS this?
Toasting brings out more flavor?
I have no idea!
It’s not as easy to load your fried egg onto an untoasted piece of bread and have an open-faced toastwich?
Also, my spellcheck doesn’t recognize “untoasted.” Perhaps the machines are smarter than we are…
Joe
My five year old asks for “toast” every morning and complains every time that it’s too brown. This morning, he finally got the bread out himself, put it on a plate, and said, “This is how I like it. Not brown.” I asked him why he didn’t just ask me for bread with butter (which is what he normally asks for with dinner). He rolled his eyes at me. I guess if it’s breakfast, it’s “toast”.
My guess is that the custom arose in a time with fewer preservatives and less well-sealed bread containers. You made bread, ate the bread at midday and evening meals, and by breakfast time on the next day, it was getting stale. Toasting the bread covered the staleness and changed the flavor slightly, making it more palatable to use at another meal.
As a result, generations of habit tell us that the taste and texture of toast is appropriate for breakfast, even if the bread isn’t stale.
We keep bread in the fridge (yeah, I know, Philistines we are). We toast it for both breakfast and for sandwiches just enough to get it above room temperature. It’s ever-so-slightly crunchier than basic stored-at-room-temperature bread, but just barely. If the color changes at all, it’s overdone.
Particularly for plain white bread I never understood the attraction of crunchy, brittle, crumb-spewing toast. Buy or make some bread with some body in it and eat it as-is. Even for breakfast.
As to why the custom for toast at breakfast, I have no actual info. Balance’s idea is plausible. My guesswork contribution is simply that in Ye Olden Dayes houses and kitchens were cold. Breakfast was meant to be hot to offset the overnight cold. So everything you served was heated because otherwise it’d have been chilled. So you are really eating hot bread, not toasted bread. it’s just that heating it toasts it as well.
This explains everything.
God, I love toast. And breakfast cereal. Especially Honey-Nut Cheerios. And corn flakes. I’d live on them, but my wife thinks I’m joking.
Try this: Rye toast. Peanut butter. Hot giardinera peppers in oil.
Or multi-grain toast. Butter. Any jam or jelly you like.
Or Honey-Nut Cheerios. Milk. Okay, that one was not complex.
Breakfast. It’s not just for breakfast anymore.
My guess is that soft boiled eggs and soldiers (toast fingers) were a breakfast for the rich. The soldiers needed to be toasted to maintain structural rigidity when mixed with the soft egg.
I have no basis for this
You never had a club sandwich? That’s toast for lunch.
Garlic bread with pasta? Toast for dinner.
A quick Google later, and I’m finding the same thing.
Toasting is a method of preserving. And it does taste different than untoasted bread. And it’s easier to spread things on.
But that doesn’t explain why it’s a breakfast food. Do we use more spreadables at breakfast?
If we do, it might have developed along with or as a reaction to the toast custom. I think it’s more that breakfast is when we’re more likely to have old bread than fresh. Having fresh bread at breakfast would have meant getting up hours before dawn to make the dough, let it rise, and bake it. It would have been much easier to toast the leftover bread, concealing its staleness, than to get up early enough to make it fresh.
What do cultures that don’t have a toast-at-breakfast custom do with their stale bread?
Make bread pudding and serve biscuits for breakfast.
Why do y’all ask? 
Well, yes–bread pudding and biscuits are both superior to toast. I was looking for something a bit farther afield, though. Essentially, I was wondering if people without a toast custom made other breakfast dishes with untoasted stale bread.
There’s milksop, of course, but the places that do that also have breakfast toast. I seem to remember something about dipping the stale bread in soy sauce with chopped peanuts from somewhere, but I don’t remember if it was a breakfast thing.
I’m liking your theory more and more. And I’m wondering if the morning spreadables thing is a case of a positive feedback loop.