Why doesn’t the baggage go on the same flight as the passenger?

Who’s idea was it that your ‘hold’ baggage went on a different flight to you? Is there really any need for such over complication?

Lets check out the facts:

* A plane can go a certain distance on a certain amount of fuel
* People weight roughly the same amount
* Hand luggage is limited in size
* Hold luggage is almost always limited in weight (as far as I know)
* If you want more hold luggage you have to pay extra and book it in

So exactly why does the luggage need to go on a different flight? I could understand if you extra luggage had to travel separately, but not the luggage that you get allocated surely!

Can someone explain?