Not always a win. There have been a few reports that sending large numbers of clothing donations to areas that don't specifically need them has the result of harming local industry that would otherwise be able to produce and sell clothes.

Assuming there was no /s there:

The US and I assume Europe have laws against "dumping" - selling a product for below cost - because it drives local competitors out of business. That is exactly what shipping containers full of clothes to Africa does.