Churches and individuals spend money that could have gone a loooong way in the third and fourth world on airfare to fly half way across the world to build and paint when local professionals could have done it for a fraction of the cost.
Many career missionaries, whom one hopes are loving and investing in those whom nobody else can or will invest in, start as short-term missionaries.
For children in orphanages, being hugged by a stranger for two weeks is better than not being hugged at all.
I have never been on a short-term mission. If I did, I would like to work with Heidi Baker in Mozambique as much for what I might be able to learn from her as for any benefit her orphans might receive from the love I will undoubtedly lavish on them.