I played for a once monthly Evensong yesterday and I had had to do quite a lot of work on the anthem and the psalm. There were some nine choir members, but no tenor, and only six people in the congregation, one of whom was my partner who had just come to support me rather than staying at home.
The anthem was quite long and probably better for another occasion, to be honest.
My feelings on the subject have surprised me (or perhaps they have not). Knowing the choir as I do they are all nice people and they tried their best. They have no way of knowing what size the congregation will be. I enjoy Evensong although the church is some distance from where I live.
To sum up, a genuine act of worship is always worth performing (the sermon was a little long) but if the trend continues I do not see there being Choral Evensongs happening for much longer.