YANBU - Major pet hate of mine.
I was in a pathology clinic recently, which shared a waiting room with patients undergoing chemo. A family of three adults, two tween-aged children and a baby came in to get the baby vaccinated. The adults left the children in the waiting room with iphones blasting some zappy game nonsense. As she handed them her phones before leaving them, the mother (I assume) said in a loud pious voice to the children "Now, there are other people here, so don't put the volume more than half way", looking around the waiting room as if waiting for compliments on her thoughtful parenting.
When I asked her to give them headphones or turn the volume off, I was accused of being intolerant of children.
No, just no. This is why people get shirty with parents of young children. To let your children make such annoying noise anywhere in public, let alone in a room full of sick and elderly people who are feeling miserable enough already, is selfish and oblivious.
Headphones, or no phone. I think most children would happily accept headphones.
To say nothing as to why those same children couldn't have been reading a book, or having a conversation, or being taken to the nearby parks or café by one of the two other adults in their party.