Why do you measure kilometers?

Answer 1

1 kilometre is the same as 1000 metres

1000 metres is the same 100000 centimetres

100000 centimetres is the same 1000000 millimetres

If you were travelling from say London to New York you would probably find it easier to write that the answer is 5571 kilometres rather than writing the answer as 5571000000 millimetres

Normally when answering a question in Mathematics it is easier to use relevant distance or mass or time that is relevant to the situation.