A factor which can affect hot and high performance of light aircraft is the pilot. The pilot either knows, or rapidly notices that the takeoff performance will be less, due to hot and/or high. This increases the "urgency" to get airborne from the available runway. The result can be prerotation, and high drag, which extends the run, and further degrades performance.
There comes a point where you determine before the takeoff roll, that you must make the most of what you have, as there is little excess. For these takeoffs, the determination of a reject point is important, and then purposefully allowing the aircraft to accelerate as much as possible, with the least drag, through each phase of the takeoff.
This is to be coupled with the other reality: Obstacles. Eventually, your takeoff path will encounter one. If it is close, all you have to do is safely clear it. You don't have to clear it by 250 feet, or even 100 feet, it things are critical. Just clear it. Refer to my thread on "Height Velocity Curve", which linked to obstacle clearance will suggest that you'd rather clear it safely with a reserve of speed and energy, than try to clear it by a much greater margin, for no good reason, and give up that safely buffer of speed and energy.
Yes, hot and high does affect performance, but so does pilot technique. Surprised and disappointed pilots like to blame the conditions, but sometimes technique played a role too....