this is my concern as well. any time I have attended an event that uses e-tickets exclusively on phones, it has been challenging. there are a lot of elements to this whole approach, some driven by the seller/event (apps, tickets on account, website), or the venue (wifi, hand scanners, connectivity to ticket/user database), or the user (presuming a smartphone), or the user's data provider (coverage) ... technology is great when it works but awful when it doesn't and it's a nightmare when it presumes all users are ready and able. and that's even without considering ticket transfers to others.
Great points.
Recent example. Two nights ago, I took my wife and daughter to the Godsmack show in Charlotte. They were playing at a relatively small outdoor amphitheater. I had bought "lawn seats" back in May when Live Nation put shows on sale for $20 "all in". I had the "tickets" in my "Apple Wallet". That wasn't an issue.
However, when we were in line, staff came around offering seat upgrades for $10. We said fine (ended up spending $30 for $55 seats when it was said and done). In order to do this, I had to go to a website, and set up an account. It offered seats, I paid via my debit card, then had to set up a PIN. The mobile web wasn't completely compatible with my 2 year old iPhone. I couldn't move off the PIN popup. It froze the entire phone's browser.
We ended up going into the venue. The LTE signal got stronger, and somehow the mobile web reset itself and the site took my PIN, and we got our upgrades.
It eventually worked, BUT, it was not a hassle-free process and did require a ton of staff around, because the same thing happened on other people's phones.