Denwand wrote:But it must work or they wouldn't do it...
It's this, exactly. Charities have limited budgets, and if they could rely on direct donations without having to pay for chuggers, they would.
Unfortunately the situation is that most people, left to their own devices, don't donate to charity. I don't have a problem with that - it's down to individual choice, not to mention financial circumstances - but neither do I have a problem with charities using direct methods like the ones you mention to ask for money.
Of course, it's totally reasonably to expect them to be polite, and not to try to apply high-pressure sales tactics when you say no thanks. Completely understand how annoying it is when they're rude and pushy.