I suppose because bread is such a big deal in Europe? Like rice is in much of Asia.
East Asia might not have emphasized bread quite as much as Europe, I suppose. China has had wheat for a long, long time, since prehistory, apparently, but the cuisines of China are so varied that I reckon the European sort of bread wasn't anything remarkable in comparison to everything else, assuming it existed there. Japanese masses only began to consume it more during the 20th century, by the looks of it.
A fair point about Spanish and Portuguese. I don't speak them, so I didn't think so far, only staring at English since the dicussing had turned to it when I joined. Europeans disagreeing with each other is the most natural thing in the world, though.
Edit: One particular thing to mention, I'd say, is that sweet bread would not have been overly abundant in the historical times. Honey was basically the only source of excessive sweetness before industrial sugar. There's only so much honey common people in the distant past would have had available. In that sense, overly sweet "bread" is quite a modern thing, mostly, apart from the experiments among the aristocracy. Otherwise it would have been up to fruits and berries to taste sweetness.