Except, perhaps, for Peter Paul & Mary singing ‘Puff the Magic Dragon’, you aren’t supposed to sing along at an entertainment performance. So those that remain silent are probably correct.
If you want to sing along, you probably should go to a worship service, not a concert (interrupted by a brief ‘feel good’ message.)
Many of our congregation listen to Christian music stations, so they like it when we sing some of the new songs. It is good to sing what we hear on the radio (we all did that in college!) However, this can be taken too far. It is good to introduce new music “before” the service for a couple of weeks. Singing is the most effective way most of us Praise God, so it is vital that all participate.