If a fire breaks out and I have to evacuate a venue, there is a _distinct_ difference in the effect on me if I have to have had my phone locked up.
In one case, I leave the facility, get to safety, and then _go home_ (eventually), at which point I have my phone.
In the other case, I leave the facility, get to safety, but my phone is either destroyed, or in a pile with 900 other concert-goers' phones, and I need to either wait around (in a place where emergency services probably don't want extra people), or _replace my destroyed phone_.
No thanks, I'll keep my phone in my pocket or backpack, and have it with me when I leave with no extra effort. If necessary, this will mean skipping any concerts or similar where that's an issue.