This is a guess but I think there is at least some historical evidence behind it. The Church lives by mission. That is if it is to survive it can only do so by the act of people who are not yet its members!
Historically the church has had a fairly broad understanding of mission. Yes it ran evangelistic campaigns but these ran side by side with social groups and welfare provision. It clothed the naked as well as preached the good news. A church was a multifaceted organisation.
Then the church realised and I think around the 1950s, that certain actions brought in more members than others. So it argued that concentrating on these were efficiency. You did not need all the suprastructure of the other mission activities nor the random pastoral visiting, nor the social chit chat with friends. What you needed to do to grow was concentrate your resources on the receptive. Social outreach could be just for the sake of helping others it was not part of the churches central mission. A very good way to dishearten the volunteers.
Lets take the old Sunday Afternoon Sunday School. Well yes that was largely child minding so the parents could have sex without the kids around or go down the pub. So we concentrated on the Sunday morning Sunday School for church children which was far more productive in terms of immediate numbers. Except that now the children end up down the pub with the adults, or some other activity (e.g. junior football and rugby clubs often meet on a Sunday). So the kids instead of learning about Christianity, learn sport or go to pubs with their parents. That means they don’t gain the basic language in which the church puts the gospel. So we are talking to people now who speak another language. Children don’t know the Christian stories any more, this is a cultural and an evangelistic loss to the church.
The problem is that many of the other less effective programmes actually created the receptive demographic. The result of not cultivating them made people feel the church was “hypocritical” only interested in looking after those who were interested in it. The church was cutting what did not suit it and not necessarily what people around wanted the church to cut.
What is more the apparent success rate of some began to make the people in the churches began to feel inadequate in just doing the ordinary things that had supported people through generations. They felt no longer able to talk about their faith because they weren’t as good as Billy Graham. Not realising that unless they talked Billy Graham could not reach their friends.
Basically the church got into harvesting and forgot to plant.
To change metaphors for the last fifty years or more, we have fished in a non-replenishing pool. The stock is almost gone and we have not taken care to see it is replenished. In other words the Church has over fished.
This is bad news because the catches are meagre now, and the only way that the catches are going to improve is actually to put resources into replenishing the stock. To do that we have to take effort away from the catching and reinvest it in all the things we gave up fifty years ago. Yes that means social outreach, yes that means social activities for people around the buildings and yes that actually means putting their desires higher on our priority list. Only there are not as many people to fish and we are not as fit as we were fifty years ago.
The good news is that there is the wider sea, the bad news is our boat is less sea worthy than it was because we have not had to keep it up to standards for the last fifty years.