sports – Why do action photographers need high resolution cameras in burst mode?

Because

-There are many things happening in a short time (movement phases of an animal or a fast athlete), and you want to shoot everything

and or

-It is impossible to predict the exact time of the event in question, so it is necessary to cover as many times as this event could occur (and eliminating the rest later).

and or

– Redundant images are needed because some factors at play may compromise a single shot (eg, other guys' Speedlites flashes, spin at a dangerous shutter speed due to insufficient lighting, extremely unwanted composition-related unwanted hazards (birds, insects, flying garbage), picture-oriented image displays you need in the photo, light-dimming schemes that can occasionally prepare you for a frame black surprise).