We were watching the program Air Crash Investigation and there was an episode where it was too late to abort the take-off and the pilots had to attempt to climb still but since an abort was not possible at that speed.
My 5 year old son asked and I quote: "If the brakes don't have enough power to stop at that speed, why don't they use the parachute brakes?"
So why don't big jets have drag chutes to help with emergency braking if there is some margin still, but not enough for the tyre brakes to stop safely in time?