I'm torn about this. I'm aware from social media that there is a thriving culture of livestreaming shows for the benefit of other fans who can't attend for reasons of cost, accessibility, health issues, or just the fact that their favourite band never visits certain countries. I think this is also a generational thing, that newer bands almost expect this, or are happy to release sets on their own social media to pre-empt it. And it depends a lot on the kind of music - at a rock gig with lots of moshing, phones are hardly going to be the distraction that they would be at an acoustic show.
In short, I do think this is a good thing, just as long as people are considerate of others around them and aren't dicks about it!