Because silence is a common good, like clean air. It's everyone's. When people fill it with their noise they effectively privatize it for the duration. When they shout on speakerphone or play their music or blare sound from their apps it's especially selfish.
I know, it's pathetic. It's partly because they don't want to pay for the staff to do the enforcement and partly probably some other reasons.
In classic British style they just try to influence and nudge people with campaigns and posters. That way the organisation doesn't have to deal with awkward accusations of racism etc
You do understand that one of those “needs”affects others around you, and one of them leaves them in peace, right?
Also I’m sure parent wasn’t referring to emergency calls
Imagine trying to live your life where other people’s desires by default overrode you own.