Since it stems from the middle-class, white belief that other races are underpriveledge and incapable of looking after themselves without help from middle-class white kids who are out there purely to boost their own sense of self-worth and look good when they return.
It's insulting. I know if I was a builder or teacher in Africa I'd feel insulted that a bunch of middle-class, soft white westerners thought they could come over and immediately do my job better with no formal training and act like they're making a big difference when in reality they're only gathering photos to show off to similar middle-class white friends back home.
The volunteers are only in it for themselves. Fact. And they are patronising and condenscending to ethnic groups they go to "help" with their own sense of superiority and belief that the ethnic groups can not survive without their help.
Plus, it does no good. Volunteering efforts should be spent in better training workers in said countries to earn a living teaching or building rather than having some jumped up, poncy kid go over there and do it for a few weeks.
Of course, many of the middle-class kids like 90% of the posters here who volunteer will refuse to see how condenscending it is and will refuse to see that deep down, they have a belief in their own superiority over other races.
I however am an intelligent, enlightened individual and I realise that volunteering abroad does not help and is insulting to the people of the other country. Plus I, unlike other posters here, don't have a belief that I am superior to the "poor, uneducated, underpriveledged" people living in Indian or Africa.