It's a complicated issue. I think the reason people donate is based on this logic:
An old t-shirt here is essentially worthless. We see somewhere that a demand exists for a worthless item (to us), so we give it to them because they are much poorer than us (rather than sell it to them). We think we save them the work for the t-shirt assuming they will be able to concentrate on something else productive rather than acquiring clothing. Everyone wins (although not necessarily the case).
In addition to making us feel better about our excesses, it makes logical sense, although the logic is based upon possibly inaccurate assumptions.
An old t-shirt here is essentially worthless. We see somewhere that a demand exists for a worthless item (to us), so we give it to them because they are much poorer than us (rather than sell it to them). We think we save them the work for the t-shirt assuming they will be able to concentrate on something else productive rather than acquiring clothing. Everyone wins (although not necessarily the case).
In addition to making us feel better about our excesses, it makes logical sense, although the logic is based upon possibly inaccurate assumptions.