Layout of darts board

Hi!
I have a darts board here at home, and I’ve been wondering dor a while now that how come the numbers have been laid out in that order.

If the idea is to get a number as far as possible from the previous number, why are 7, 8 and 9 so close to each other?

Link. That’s not very helpful and further googling is not reavealing much more. Good question though.