When there’s a gap or a hole we have the probability of filling it in. But by the word filling comes the word fitting. Yes, a filling should be fitting. This is the simple logic why tooth-colored fillings is often used nowadays than amalgam or the gold fillings.
Tooth-colored fillings or composite resins look more natural. It blends to the teeth that is why patients are choosing tooth-colored fillings rather than the gold one.
Studies, however, said that composite resins are less durable compared to amalgam and more costly.
Nonetheless, people still choose to have their teeth in plain white. Cosmetics really matters, in short.
https://www.youtube.com/watch?v=pa0MVT0Zbcc