I have no horse in this fight, but just off the top of my head agreed on standards for p2p file transfers. A baked in utility that makes sending and receiving files would go a long way towards bringing the feature to every day users and the standards mean the power user can send and receive files from their favorite CLI or choose from one of many paid and open source options. Both users can send and receive back and forth to each other without having to agree upon a third party client, or without a client at all.