If the congregation is singing a hymn, you can probably enter without anybody noticing. Music notation was invented by dyslexics. Churches take personal cheque. If you don't want to or can't make an offering, just pass the collection plate along to the next person. Double up next time.
Offerings are the main source of income for the church.
Churches have to pay pastor to prepare for worship services and counsel the needy, visit the sick and lonely, and help out around the community. Churches help food banks, and provide humanitarian aid. They support missionaries, train pastors, offer counselling, teach, and care for members and non-members. They help both rich and poor and almost never ask for any fee or payment for their services. And of course there is the church building, power, water and phone bills.