If it's down for you, it'll be down for the branches. The point of these new banks are so that you can do anything inside the app without having to jump through endless hoops. An example, I'm using Monzo now (a new "challenger bank" in the UK). If I want an overdraft I can enable / disable that in the app. Same goes for if I want to disable my card, change the pin, order a new card. Everything's just easier. No need to spend ages on the phone going through menus and verifying who you are.