MB
If all engines are operating (which thankfully is usually the case), there must be 15% additional runway remaining at liftoff.
If an engine failed at V1, and you crossed the end of a 10,000 runway at 35', then in the case of AEO, you would liftoff approx. 1300 feet sooner.
Sometimes it "seems" like we're using every foot of it, though. A slow rotation rate makes it look worse than it is.