It's deliberate in most if not all cases ...
Originally Posted by AC-25-7A guidance
10. TAKEOFF AND TAKEOFF SPEEDS - §§ 25.105 AND 25.107 (PART 25 AS AMENDED THROUGH AMENDMENT 25-42).
(5) Section 25.107(d) - Minimum Unstick Speed (VMU).
(viii) VMU Testing for Geometry Limited Airplanes.
(B) The criteria for demonstrating the capability for a clean liftoff and fly-away are as follows:
(1) The airplane’s pitch attitude from a speed of 96 percent of the actual liftoff speed must be within 5 percent (in degrees) of the tail-dragging attitude to the point of liftoff.
(2) During the above speed range (96 to 100 percent of the actual liftoff peed), the aft under-surface of the airplane must have achieved actual runway contact. It has been found acceptable in tests for contact to exist approximately 50 percent of the time that the airplane is in this speed
range.