Why? Three basic reasons:
I Don't Like the Interruption: When I'm working, eating dinner with my family, relaxing, I don't need the phone to be ringing with somebody asking for money.
It's Probably Not the Actual Charity: Very often the person making the call is working for a professional fund raising outfit that may be taking 80% or more of the money raised. When that happens, I can hang up the phone, go on line, and give directly to the charity - and the charity ends up with a lot more money.
Fraud is On the Rise: We've seen any number of "sound alike" charities arise, using names similar to established, quality charities in order to elicit contributions from confused donors. But we are now seeing overseas phone banks set up, pretending to be actual charities, soliciting donations by credit card and then using the credit card numbers to engage in fraudulent purchases.