If you have an HDR monitor, calibrating it would straightway improve the overall viewing experience. It will improve the video quality when you are watching HDR videos. Also, monitors generally do not perform well when viewing a video's bright and dark parts. The brighter part gets brighter than the maximum supported brightness of the display or darker than the minimum supported brightness leading to a clipping effect that reduces details in bright and dark areas. But when you calibrate your monitor, it balances out the overall scenes in the brightest part and darkest part of the video.