Heck, I don't even go to church, but I bet I can come up with some reasons for trips like this.
- Immersion. Gets people away from conflicting local
influences. You're surrounded by a team with a stated
mission and supervised activities for a period of time.
Fewer distractions, more ability to discuss what happened
and retain behavior and beliefs in months and years to
come.
- Bonding. Encourages bonding as part of a group.
You become a member of a team, and take its memes on
as your own. You know what happens in Army boot
camp? This is a lot less rough, but odds are, it's
developed with some of the same goals of building
fellowship, team, beliefs, unity of purpose, etc.
- Culture. Even if it's just Houston to Seattle or
Los Angeles or Philadelphia or Albany -- travel has
benefit. I can guarantee you that the culture -- and
sights -- are a lot different in most parts of the
country than "home". The people who go on these
missions will have the chance to get exposed to some
different things even in the same country. How much
is that worth? I don't know... but certainly it's
worth something.
- Focus. Sure, they could do the door-knocking,
homeless-feeding, shelter-building in their own
communities. But do they in practice? It's hard
to get most teens to devote a day to something
like this... but here's a chance to get them to
spend a week on not just socially acceptable, but
possibly socially beneficial things, while they
learn a bunch and get all the 'benefits' listed
above. Isn't that worth something?
- Peer pressure. The Bible says that "A prophet is
without honor only in his hometown." And, until you
have a real fire in your belly, it's also *hardest*
to be a prophet (or missionary) in your home town.
Shoot, I can easily get up the courage to make a fool
of myself going to preach to folks I won't ever see
again... but... if my friends from school might see
me? Yikes! And the people you meet in that new town
will also be more likely to listen to you because
you traveled a thousand miles to see them.
- Program. From the church's point of view, this
kind of thing is part of a program that they market
to potential and actual members -- "Look at all the
cool things we do!" And maybe it's a benefit to
the mission leaders that they get to get out of town
for a while every year, too -- although my guess is
that many of them come back with a lot less hair (or
a lot more gray!) than they left with.
Now, I don't know if you should give her money or
not, but I hope this helps you understand why the
programs exist. If you still don't think that the
church should be sending people off to Timbuktu for
missions, then I encourage you to get with the
leadership of your church and let them know.