The reason(s) why a tall athlete commonly has more problems performing a full squat is/are due to:

A tall athlete often encounters challenges when performing a full squat due to a combination of factors related to both height and bodyweight.

Height plays a significant role in squat mechanics. Taller athletes typically have longer limbs, which can alter their center of gravity and how their body moves during squatting. This can lead to a greater distance that needs to be traveled during the squat, potentially making it harder to maintain balance and proper form. Additionally, longer femurs can affect the angle of knee flexion and the alignment of the hips, impacting the athlete's ability to squat deeply without compensation.

Bodyweight is another key factor because it contributes to the overall load being lifted. If a tall athlete has a higher bodyweight relative to their stature, this can increase the difficulty of performing a squat as the muscles need to generate more force to overcome the weight of the body. Additionally, excess bodyweight can lead to biomechanical inefficiencies that make it more challenging to achieve the full range of motion necessary for a proper squat.

Flexibility is important, but it does not fully encompass the difficulties faced by tall athletes. While flexibility in the hips, ankles, and knees is critical for a deep squat, the mechanical disadvantages and weight considerations due to height and bodyweight are more