BECAUSE NOT ALL EXERCISES ARE FOR EVERYONE.
Some individuals may struggle to perform certain movements due to factors such as biomechanics and mobility. Someone who is tall for instance, who has long levers, may be more suited to doing sumo deadlifts as opposed to conventional, simply because of the distance they would have to travel, compared to someone who has shorter levers. Many people for instance, may struggle to achieve the correct starting position in a deadlift due to limited pelvic mobility, therefore an elevated deadlift may be more appropriate for that individual.
Below you will find some adaptations that you may find useful, and may allow you to still perform an exercise, while you work on addressing any mobility issues you may have, if that's where your limitations lie.