The nice thing about the old world of music was that when you played for an audience there was nothing going on but what you were doing. Now the band has to compete with everyone's phones.
That doesn't seem like it should be that hard. You are at the concert experiencing the concert, which should be pretty instant and gratifying. Either you like it enough that you don't miss your phone, or you decide that the concert experience isn't what you're looking for.
Being at the concert but doing something else seems like they are doing it to say they were there, and there are are always other ways to signal status people can fall back on.
Another thing - you could sell music (ie. records / CDs) at gigs. You can still just about do that but probably not for long, at least with most markets. A small independent band will likely make more profit on a single CD sale than they'll ever make in downloads.
Records nowadays have an mp3 download code with them. The physical media of the record is almost just a placeholder, now, but people still like that even if they don't have a record player (!).
Same thing could apply to some other object. I've seen it done with USB sticks and business cards. Some sort of physical media is still useful for that purpose.
I'm not sure that makes as much difference as you think. You're still performing (generally) for an audience of people who chose to spend their time and money to come see you play. You've already got them. They may peck at their phones occasionally, or not, but your music is the reason they're here.