Companies should make their products available in several ways to give their customers a choice. That does not mean every possible way but trying to get everyone on the smartphone is not good service.
A couple of years ago, I dropped a friend off in LHR T5 for a long haul and proof of Cv19 vaccination required at check in. She opened her Smartphone but could not get a signal. The data is stored centrally to prevent as much fraud as possible. So I switched my Smartphone on to make a 'HotSpot', this means that my phone is connected to the network but allows her phone to connect to mine and use my network temporarily. It all worked and we apologised for the delay.
On more than one occaision at JNB international departures, I have not been able to get a signal to my phone for check-in. OR I get the pass on the phone but, by the time I get to the head of the queue, the screen has blanked to save power - and I then cannot get a signal to refresh the screen.
So I always take printed paper along with me. The same goes for hotel and car bookings. ANYTHING I book before we leave home is in my carry on. When I get home, the paper goes into the recycling.