Japanese audiences are said to be quiet at concerts.
Why Japanese audiences don't sing with singers at concerts?
Because they want to hear and respect the singer's singing and talking voice, they don't want to hear the audience's voice.
But if a singer said them to "singing!!", they will sing.

Tokyo first show…   • 【Full】Taylor Swift Reputation Stadium...  

1, ...Ready for It?
2, I Did Something Bad
3, Gorgeous
4, Style / Love Story / You Belong with Me
5, Look What You Made Me Do
6, End Game
7, King of My Heart
8, Delicate
9, Shake It Off
10, Dancing with Our Hands Tied
11, All Too Well
12, Blank Space
13, Dress
14, Bad Blood / Should've Said No
15, Don't Blame Me
16, Long Live / New Year's Day
17, Getaway Car
18, Call It What You Want
19, We Are Never Ever Getting Back Together / This Is Why We Can't Have Nice Things