Is it recommended to have one crown cover two implants?

Hello. I got 2 implants, and a bone marrow. Everything went well. I got my crowns too. I got them together. Tooth 5 and 6. Dr said it's better that way.. but he also seemed confused when I asked why both crowns came together? The question is when would be a good decision to put 2 crowns together as 1 tooth for 2 implants? We didn't close the crown yet. Thank you