Why do so many breakfast dishes across so many cultures have dessert like features while lunch and dinner dishes do not.

I guess the question to that question is: do they? There aren't actually a lot of consistent features to breakfast cross-culturally, and those features that are common are usually more about how easy the food is to prepare than how it tastes. Certainly Western breakfasts, particularly American breakfasts, do tend towards the sweet, but even that is far from a hard and fast rule, and in some cases things that present as sweetened in one culture may not be that way in others. For example, porridge/oatmeal is commonly a sweet dish in the United States, but was traditionally savory in Scotland. In fact, American cuisine (breakfast included) is sweeter, on average, than that any other country for reasons that, at least in the books I've read, have not been conclusively addressed at this time. We also need to ask why Americans eat the things they do for breakfast, I think.

If we go all the way back to medieval England, breakfast was not a common meal. The main meal of the day was "dinner", the midday meal, which was generally served much earlier than our modern conceptions of midday, about 5 hours after rising, at around 9-10 AM. People expecting to perform particularly heavy manual labor might scarf down something very basic to enable them to get through to dinner. Nobles might eat something more elaborate, but it was still a light meal. As time went by, dinner became somewhat more involved, and moved later in the day, requiring a larger intake of morning calories to be able to work effectively. As in many parts of the world today, this more substantial (but still relatively minor) morning meal involved leftovers, griddled cakes (pancakes... if you will), preserved ingredients (salted or smoked meats, fish, eggs), or other things that were easy to put together and were calorically dense. Similar patterns of consumption continued into Colonial America. None of these foods were considered "breakfast" foods at this time, they were just foods, that you could eat whenever, and happened to be convenient first thing in the morning. A bowl of pottage or soup was just as good as anything else, if you had it sitting around. At the same time, apple pie was fair game for dinner or supper, if that's what you had.

Where this started to change was during industrialization. An increasingly urban population in the United States was adjusting to a new mode of living very different from the agricultural lives they or their parents had known. The regimentation of work and lack of time to interact with others led to meals acquiring specific, modern, meanings. Breakfast being about preparing for the day, lunch about tiding over until the evening, and dinner about spending time with the family. Dishes began to be segregated into categories that served these purposes: so a sandwich is a classic lunch food because it's portable and easy to eat without mess. But why are the foods that became breakfast foods, breakfast foods? Mostly persuasive advertising. Traditional diets that served the needs of agricultural labor created well... a lot of constipation and bloating in a relatively sedentary population of urban factor workers. Health food purveyors, particularly in the US, claimed that that cereal, simple and grain based, would alleviate that. It proved to be a persuasive pitch. After the Second World War, to appeal to children, a whole bunch of sugar was added to traditional cereal recipes and the modern cereal market was born. Cereal also served urban capitalism's demands on people's time: it was extremely quick and easy to eat, convenient not because it was available, but because it was fast. Pancakes made their way into the breakfast canon for similar reasons, especially once box mixes started to become common in the late 19th and 20th centuries. And adding sugar to box mixed helped them sell. Commercial waffle irons did the same thing for waffles, previously more of a dessert or dinner food. After a certain point, by the mid-20th century, there was just kind of a momentum to it. Things are breakfast foods because that is what breakfast foods are like, and a relatively static conception of breakfast was present in America. They were sweet because they were largely based on heavily grain based foods of a sort that people had liked to sweeten when possible, and sweetening them consistently made sense for mass-produced, commercial products in a market with sugar prices that had plummeted dramatically from their luxury-product enforcing heights in previous centuries.