Millions of people in America (and other countries) sing in church choirs. Most of them are not trained musicians, and most of them do not possess a skill at sight-singing. They learn the music by having the part played on the piano or organ, or having the director sing their part. Imagine how much it would help each individual, as well as the whole choir, if many or all of them learned how to sight-sing!
At the outset, there would be a tremendous saving in time. If every member of a choir could read the music at the beginning, all the time that's spent in demonstrating the parts could be saved. No longer would the director have to show how each part went, and then repeat the process the next week. The singers would be able to sing, more or less accurately, the first time they saw the music.
What could be done with the time saved in this way? It could be used to go either deeper or broader into the music. It could go deeper by allowing more focus on the musicality, the nuances of the song. This would elevate the performance skills of the singers, as well as the skill of interacting with the congregation. The effectiveness of each anthem would be increased. The time could also be used to go broader, learning more songs and singing more often. This would perhaps double the ministry opportunities of the choir.
Of course, during the intermediate stages, some members would develop the skill before others. The director would still have to demonstrate the parts for the benefit of those without sight-singing skill. But those who had the skill could help the others learn the parts, as well as learning the skill. When those with the skill constituted a majority, the others would have someone to lean on, and the choir would be swept along at the pace of the confident ones.
Besides time, another benefit gained is accuracy. For singers who don't have the sight-singing skill, there are going to be inevitable performance errors. Even with the music in front of them, they will sing some passages wrong. Those with the skill are much more likely to be able to sing every note correctly. This would cause a great improvement in musicality for most choirs. The congregation would benefit as well, as the overall sound would be more pleasant to hear.
An added benefit to each individual singer who gained this skill would be an increase in confidence. He or she would know that the right notes were being sung, and there would not longer be the fear of getting up to sing and not knowing the music. This lack of stress would improve the well-being of each singer, and the presentation of the choir as a whole.
A final benefit of a sight-singing choir would be the added flexibility it would bring to sing songs on the spur of the moment. Many pastors don't plan their preaching schedule very far in advance, and the choir often has to begin preparing songs with no knowledge of what the pastor will say in the target service. If the choir could prepare an anthem in a week or two, it would have much more flexibility to change anthems to match the theme of the sermon. It would also be possible to interpolate songs with very little notice, based on events in the congregation or in society at large. The options are always more numerous when the choir can sing a song with little or no practice.
If the typical church choir could find a way for all of its singers to become skilled in sight singing, it would have many benefits for the singer, for the choir, and for the entire congregation. It might take an investment of time in the short run, but it would pay off many times over in the longer term.