They are a middleman and do take a slight overhead, 1.1% last I saw, but it might have changed since then. The benefit is one of simplicity. Many people want to give to charity and aren’t sure which one. UW let’s them donate one place and it get distributed to many. They also have criteria that charities must meet to qualify. Also, like you mentioned, they do the paycheck deduction. All of what they do is about making it easier and hassle free as possible to donate, making it more likely that people will.