One of the difficulties with being a minister is that well over 90% of the congregation is 'volunteer labour', that is they don't get paid. They often help out with cleaning, cooking, opening their house, practicing music and playing in church, helping out with the preaching, business administration; the list could go on. On top of that they are also expected to contribute financially; the tithe.
Depending on the Church is the level of expectation that members will contribute::
It would appear to me that evangelical/pentecostal church pull out 'its in the bible' to get very serious contributions especially around the areas of tithing.
When I look at my Church which is the Uniting Church this doesn't come through in an upfront manner, through the pulpit. It seems because of the older age of the congregation it is something they have always done. Helping out not necessarily because of biblical reason but just because it is the right thing to do. (It maybe different in other Uniting Churches with younger congregations)
Its strange but I've never seen a group of people contribute as much as in the Uniting Church but they miss out on one vital ingredient of the pentecostal and evangelical. The desire to convert people to their 'belief'.
I wonder if this is one of the reasons why the Uniting Church is decreasing? Probably, but I like the non-cohesive nature. It feels more genuine. Overall the whole idea of giving back, being a non-paid volunteer is a good thing; been part of a team for the common good. I'm not sure you need a to detailed reason other than it is the right thing to do.