Why is decimal number 10 represented as 0001 0000 in BCD(binary coded decimal) and not 1001 in BCD?

Question

As we know BCD is weighted as 8421. If we just place 1010 it becomes 10. But in reality its 0001 0000. Why is it like this ?

Answer 1

Because in BCD, each group of four represents one decimal digit. So the first four bits can only be used to represent 0-9, even though they COULD represent anything up to 16.

Why was it done this way? Probably to make it really easy to read off the decimal equivalent of the number, without any "carrying", etc.