Countryboy has the number one reason.

Another "Byron" thing to consider. Sometimes the plane gets sucked to the ground due to the cheater hole. You may need to pull back on the throttle a bit, after rolling at full speed, to get off of the ground. The problem with this is you need to get right back to full as soon as you break ground.

Also, keeping up in during your roll will help with your steering.

Mark M.