SNS3Guppy

The answer to your question really depends on what it is that you're doing with the airplane, and why, as well as the type of airplane in question.

If you're flying a light single engine airplane from a grass field, there's really no refusal speed, no decision speed, nothing of the kind. Simply one needs enough room to get the airplane into the air and go fly. If one has an engine failure, it's really little difference between having it on the runway, and gliding to a runway; it's part of planning for a takeoff in a light, single engine airplane. In general one should plan on having ample room to reject the takeoff...but at what point? In a light single, the action of the airplane, and of the pilot is fairly much the same at any point should the engine fail...the airplane is going to return to earth and stop, no matter what. Planning a takeoff in a single engine airplane, then, includes having available places to go beyond the runway, as well as on the runway itself, should an engine fail...the world becomes a forced landing site, or one big runway, if properly planned.

Not so for multi engine airplanes...but not for all multi engine airplanes. As airplanes get bigger they land faster, are heavier, and fare less well with both a forced landing and a rejected takeoff. In fact, as airpalnes begin to get larger, their brakes don't get much bigger, but they get a lot heavier. Decisions to reject become more and more critical, and as airplanes get bigger and more complex, and have more power, the options with regard to what to do after takeoff increase.

In a light twin engine airplane, failure of one engine often means the airplane will be descending to earth just like the single engine airplane...80% of it's performance is gone when one of two engines quits...because much of the remaining engine is left fighting drag and assymetry issues, and because climb performance is based not on the thrust required to fly, but excess thrust...it's just lost all the excess, and much of what was required to maintain level flight. It's coming down, too.

More importantly for the light twin, it has assymetry issues...should an engine fail, the other engine tries to push the airplane into a turn or yaw, and also into a roll. This force can be quite powerful, and can result in a loss of control. In some cases, the only choice may be to remove the power from the "good" engine, and land anyway. Due to the increased landing difficulty, and control difficulty, and stopping difficulty with the increased weight of the multi engine airplane, allowing excess runway is prudent. It's prudent for two reasons, and these directly apply to larger airplanes, as well.

Longer runway than needed is prudent for stopping, obviously; if one reaches a given point on the runway and needs to reject the takeoff, then one still needs the distance to do so...but just as importantly, if one elects to continue the takeoff, one may need a clear path ahead with which to do so. In comes the takeoff distance and clearway which permits continuing the takeoff...nearly always the safest thing to do in large, capable airplanes, nearly always the foolish thing to do in a light twin (and certainly a single engine airplane, in which one has no options).

I've flown several types of operations in which we regularly used all the pavement. Or gravel or dirt. All of it...from one end to the other. I've done this in single engine and multi engine airplanes, both small airplanes and large. The reasons for doing so have varied from very limited terrain in which to place a runway (small, one-way dirt strip in a box canyon, for example; tall cliff rising at one end, deep canyon cliff falling away at the other...and nowhere to increase the runway length), to operational necessities such as emergency operations, etc.

In transport category operations such as corporate and airline, it's a little different, and considerably more structured. One plans at a minimum to be able to stop in an emergency, and to be able to go and reach a minimum height and have a minimum climb gradient with obstacle clearance for all takeoffs. Considerable regulation applies, and the practices, policies, and performance requirements are nearly universal globally in this arena.

This is not necessarily the case for other types of operations. Some may wince at the concept of using all the runway in a firefighting operation, or a relief operation, or a back country or bush operation...but the truth is that very often that's all you've got, and you use what you've got. When there's a beach to land on and takeoff, you're never going to get more beach. If it's a single engine airplane with the engine failure on takeoff, there's little difference if it fails thirty seconds into the takeoff or 30 minutes...and one isn't getting a longer beach, a paved beach, or one with facilities. It's just the beach.

In hauling heavy loads off short runways in firefighting, we always had the advantage of a disposable load, and I've had to jettison it before during an engine failure or other emergency. Doing so on the runway isn't practical as it tends to coat the brakes and make stopping nearly impossible anyway. Once one starts the takeoff, one's committed, and the result is that the only concern during the takeoff is obstacle clearance at the end. I've flown tankers on fires out of relatively open fields such as McCall, Idaho, or Hemet, California (USA), where much, if not all of the pavement was used, and in the case of McCall, one had to maneuver to avoid trees and cows off the end of the runway. Stopping wasn't an option. I've done it in single engine and multi engine airplanes.

I've also flown passengers out of those locations, too. In each case, I took into account the full takeoff performance regime, including with and without all engines operating, and planned accordingly. I didn't use all the runway, allowed for stopping, and allowed for a continued takeoff with an engine failure. Just last year I operated out of McCall in a single engine turbine tailwheel airplane, hauling retardant onto wildfires...and I again used all the runway and just cleared the obstacles with a turn, due to the weight and requirements of that particular assignment. I used less than my maximum weight, because the performance of the day wouldn't permit it...but used all the field none the less due to density altitude (reduced performance with increased temperature and altitude).

Bottom line is that sometimes it's acceptable and appropriate, and sometimes it's not...one needs to consider what it is one's doing, with what, and why.