Tail strikes happen.
• Too early or too late rotation
• Too fast or too slow rotation
• Excessive rotation rate
• Excessive initial pitch attitude
• Rotation at incorrect Vr for the weight and flap setting
Even putting a non pilot passenger in the seat and giving effects of controls. (not this operator, one much closer to EASA land).
The crew don't always know that it has happened, there is 13" and 1.5 degrees between a normal Flaps 1 takeoff and touch. Some aircraft have a sensor to indicate contact has occurred, and will annunciate that in the cockpit, others only show up post flight.
More tail strikes occur on landings than takeoffs.