Why most hotels serve a continental breakfast.
It depends on where you are, but in most Western countries, continental breakfast is cheap for the hotel.
Most of the food you see in the picture above can be easily purchased in bulk in most Western countries. They aren’t expensive, either. Maybe the most complicated one is the bread, because you need them fresh. But in most Western cities, you wouldn’t have much difficulty to get such breads delivered at 6 - 6:30 AM every day, ready for serving at 7 AM.
Besides that, in Continental European cities, those are indeed what people eat for breakfast in real life. If you have a Western European business traveller staying in your hotel, he would appreciate having breakfast familiar to him, which he knows he wouldn’t get a stomach problem during the day.
And lastly, the continental breakfast is flexible for people with some dietary requirements. A vegetarian can easily avoid the cold cuts. A vegan can eat the breads with jams and juice and coffee.