If a user has capable to send files ie. photo, video, etc... using Facebook Messenger and the receiver can view it on either mobile app or PC, why cannot view files on portal?

Looks like your friend send you photo via Skype, you can view it on Skype mobile app but cannot view Skype on PC. How logical that the same Skype doesn't work together in different platforms?

Same as Messenger & Portal as platforms, these are under & owned by Facebook. When I send photo via messenger must also be visible to portal. So why doesn't work on different platform ie. Portal?