Just to clarify, it was left out from pretty much all the 4 points that were mentioned by @JonMikelV, good guessing 
And there are two other reasons:
5. I figured that those who really need it know what a path looks like and can paste it.
6. It is better to run the backup from the machine where the data resides. It is much faster.
That said, we can add it easily. The UI is a browser UI, but the webserver that runs it is a normal program that can scan the network.
Maybe it should always include some kind of date, like “tomorrow” or “in 4 days” ?