Front to Back Axis Level - Does it matter when installing a Riflescope?

This video explores the implications of having the front to back axis of the rifle / rail level during the process of installing an optic or riflescope. If the rifle will be angled during shooting, why would there be any need to level that axis during the installation?
Featured in this video:
Masterpiece Arms 6.5 Creedmoor BA Rifle
Masterpiece Arms Competition Chassis
I am not sponsored or affiliated with the manufacturers featured or shown in the video and all equipment shown in was purchased by me. The information provided is for entertainment purposes only.