Volunteer what?

Surprisingly, there aren't many travelers in Nairobi. Or I should say "independent backpackers". There are two types of foreigners in Nairobi: volunteers and dive-in and out tour groups. Most young people I met in the Youth Hostel were working in Nairobi as "volunteers". These young men and women traveled from Europe, Asia and US to Nairobi for some volunteer work ranging from one week to several months at their own cost. It's quite popular in UK that high school graduates take a year off to travel and work as a volunteer in this part of world. It's obvious a great experience for them. They show their compassion, enthusiasm and excitement on their face. A 18 year old German girl had some pretty interesting volunteer experience including several months of mid-wife (helping local women give birth) in a remote rural area and building a business partnership with a supplier for the water system in a small village in the south of Kenya. When I met her in Nairobi, she had stuck in Nairobi for a few months to get her visa renewed. She later ran out of money and had to move in a local's apartment. She seemed happy to hang out with another German girl and she told me she would like to move back to Germany soon after a year of staying in rural areas as the only "white". Why wouldn't she? When being asked about her experience in Africa, she didn't elaborate much on the details of her ventures. I wonder why a small African village need to bring out a white teenage girl who has never gone through the labor herself to help the village women with labor or expect such a high school kid who has no business experience nor speak their tribal language implement the water system for them. I also wonder what the 18 year old got out from her one year tenure in Africa and what memories she will take with her back to her own country. I didn't get a clear answer from her.
Another volunteer scenes I came cross a number of times is a white young girl holding a black African baby with a passion and love on her face. There's absolutely no doubt that African children are lovely. But again, I don't quite understand why these "unfortunate" local orphans need to be held and loved by white women given the fact some of them do have their own mothers and aunts, if not, many loving African women have no jobs and badly looking for some small paid jobs like this? A Polish girl I met in the Youth Hostel came to volunteer at a local orphanage initially for one week and later decided to extend for another week. The total cost for her two weeks volunteer work can afford an average African family to live one year or hire two local women for one year to work in that orphanage.
The volunteer myth followed me throughout my rest of trip in Africa. To fully understand the volunteer culture, I got an opportunity of working at a " orphanage/nursery school/boarding school" for one week later on in Uganda. The myth was unveiled.