Speaking to OXM, Microsoft Studios boss Phil Spencer revealed that even as late as E3 2013 there was discussion about whether the company "could get away with" removing the disc drive, though ultimately the size of games meant it didn't make sense.
"So we decided - which I think was the right decision - to go with the Blu-ray drive and give the people an easy way to install a lot of content. From some of those original thoughts, you saw a lot of us really focusing on the digital ecosystem you see on other devices - thinking of and building around that."
One of the big issues many people have with digital-only games is one of ownership: having a physical disc confers a reassuring sense of possession for gamers that games you purchase digitally can often lack.
It's likely the final decision had something to do with the company's about-face on many issues last year, especially the revised decision to allow Xbox One owners to play the console without an internet connection.