That's an interesting perspective, and I'd be interested in seeing whether people who go on these sorts of trips end up giving more on average to charity across their lives than people who don't. If so, then the trips could be worth encouraging as a societal norm, not for the good that they do directly, but for the impact that they have on later donations. If the trips don't have much of an impact, then it would be better to discourage people from doing this, and societally encourage donations instead.