Getting transactional with charity is the whole point. That's why religious organizations often fight against public programs instead arguing that religiously affiliated charity should take its place (receiving public funding to do so in many cases).
Utah in particular loves to under-fund programs, and let the church pick up the slack. The benefit to them is that it is both transactional, and allows them to exclude as they desire.
The Mormons might be nice, but they shouldn't be getting public money to provide public assistance. They should be cut out entirely and taxes should fund these programs directly and fairly.