I always shoot with 2 cameras. Equipment fails. That’s a fact of life. Each of my cameras hold 2 memory cards. I always save the photos to both, that way, should a card fail, there is always a back up.
Another reason for using 2 cameras is the different style of photo they offer. I use a wide angle on one – which gives great shots on the beach. It really helps capture the wedding ceremony against the backdrop of the amazing beach on Fanø. The second i use a 70-300mm zoom. This enables me to get close shots, but without getting in the way – that makes the photos more natural.