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Yes, there is something arrogant about that -- which is why it's important to go in with the realization that they may very well do more for you than you do for them. Service is not a one-way street; it's a relationship, a chance for two very different worlds to meet and try to understand each other.
The attitudes of individuals on the trips don't negate the value of the trips themselves. (Though some trip organizers may encourage that attitude more than others.)
I agree very much with the bolded, and that's been my own experience coming away from my international work. What I've taken away from this work has changed me immensely, and (I hope) has better equipped me to do something more substantial in the future.