I throw the tickets into my (digital) wallet and then don't think about the app until the next time I need to buy tickets. But that's not helpful if you don't have a phone.
I used to print paper tickets so I could get into a show if my phone died / got broken / etc. That doesn't happen often, to be sure, but I also don't want phone bullshit to keep me out of a show that, in the case of this recent one, I have >$500 in tickets for. One less dependency is a good thing.
More to the point, the app isn't for my convenience. It doesn't do anything to make my experience better.
Most e-tickets designed for wallet apps follow a well understood standard which has multiple implementations available for different OSes, e.g. https://linuxphoneapps.org/services/pkpass/
More to the point, the app isn't for my convenience. It doesn't do anything to make my experience better.