I am the bookkeeper for a church. The reason the letters are sent out is to get an idea of the projected income for the church. It would be really hard for you to be able to budget if you had absolutely no idea even an estimated figure of what you would receive for the year. We can't decide to buy a new copier or to buy envelopes without making sure we can pay for it. We rely on God to provide, but those provisions are given from congregation members. Usually when God comes through, it comes in the form of a check from someone from the church
Our church has a stewardship drive once a year, to get an idea of general fund donations. I enter those in and send statements once a quarter to let people know where they stand, because for a lot of people, it's very important for them to know if they have paid their pledges off or not. It's not so we can guilt them in to paying their money or make them feel bad for not paying. The church can usually make up a shortfall from a pledge from other income coming in and NOTHING is ever said to those who don't fulfill their pledge. I'm the ONLY one who knows, and I don't even pay attention to it when I do statements.
There are never any recommendations on how much you should give, no percentages listed or anything. Tithing is a personal decision, and not everyone is in the position to give 10%. I have one older man who sends in $1 cash every week. EVERY WEEK. He usually includes a little note about how he wishes it was more. I caught him one day at the office and told him what his $52 a year could pay for (office supplies, 1/4 a phone bill). That's what it's about. If everyone could at least give $1 a week....
We also do a missions pledge once a year to give people an opportunity to donate to missions the church supports. Once again I keep track in the computer and send statements, but I don't call people if they don't fulfill their pledges, and I don't tell the pastors that so and so hasn't paid.
I think people need to remember that church's are listed as Not-for-Profit for a reason, because being a daily bill payer at a church, I can guarantee there isn't a profit at all. What comes in goes right back out, and anything extra is put towards helping the community or other missions.