But I'm fine with a power bank or charger in my bag/pocket (which in reality I never need as I'm usually home after 10-12 hours with over 50% left).
I usually need a power bank at the end of my day as it usually runs to 15% of less, even with a new phone. The map application on my phone consumes a huge amount of battery, and it is the thing which I use the most when taking transport as I have to plan my route and see where I need to get off.
Which means it needs 1% battery (it'll last ages on this level in flight mode) and for the screen to work. Other functions can be broken, e.g. you don't need the NFC, the audio functionality etc.
What you said was gross hyperbole.
The closest I got to flat battery on my phone during a train journey was after an orienteering race which used MapRun 6 as the punching system (i.e. GPS orienteering). I forgot to bring my portable charger, however I had brought a spare phone. My primary phone with my Railcard loaded dropped to 2% so I took the SIM out and put it into my spare phone, which had 20% left at that moment. However, within minutes, it dropped to 5% as well as I checked bus times in a rural area, and I had to download my digital-only 26-30 Railcard onto it as well. By the time I boarded a train, one phone was already dead and the other was only 1% left, and I still needed to check which station I had to got off the train in order to get a bus home (I was not familiar with the transport network in that area - I lived at a place not close to railway stations and I parked my bike at West Hampstead and planned to take a fast train back to London to pick up the bike, but my journey was delayed and I missed the fast train, and waited for half an hour for the next slow train so I would like to get off the slow train at an intermediate station where I could take an express 232 bus direct home to make up time)
I tried to ask other passengers where I should take the 232 bus but no one knew, and I had to brought my phone out of flight mode at 1% to check TfL website. Unsurprisingly during the journey it went flat, and at the time I exited the train, both phones were dead, but fortunately there was no ticket inspection to check my Railcard and I used a paper ticket for that journey, as e-ticket wasn't available.
I honestly don’t think TVMs will be around forever so it’s pointless making one that prints eTickets from a code.
If you need a paper ticket go to the ticket office.
I honestly don't think ticket offices will be around forever, as TfL has already got rid of them. We can't expect that everyone can buy tickets on mobile or print them out beforehand, so ticket machines will still always be needed. If you need a paper ticket go to the ticket machine. And in the future, these machines will sell tickets in a form of a code printed on a piece of paper without any magnetic, as magnetic is an outdated technology and prone to failure.
If we remove all ticket machines instead and force people to use the ticket office, we can feasibly expect dozens of people queuing at every major regional station.