The old adage comes to mind that runway behind you is useless when taking off.
I operated out of Darwin for many years and while no one will stop you using full length you wouldn't make many friends creeping back to use full length in an aircraft that can t/o in a quarter of Darwins length.The busy departure rate would plummet and holding fuel would increase. Imagine the thoughts of a 747 crew inbound from overseas when told to hold due Cessna 150 backtracking so he can use full length.