It's weird, only really the US and Canada have such low profile cities as their capitals.
Japan's capital is Tokyo, France is Paris, UK is London, South Korea is Seoul, etc.
Essentially the biggest city or one of the biggest cities tends to be the capital city everywhere in the world except for North America.
EDIT - It's probably just due to the nature of our countries and/or colonies being formed before they were developed. Also a lot of other countries moved their capital cities after war or revolution events which we haven't experienced.
EDIT 2 -
https://en.wikipedia.org/wiki/List_of_purpose-built_national_capitals I guess there's also countries like Australia that have same thing.